PDSTUDIO DESIGN SYSTEM AND METHOD

[0001] This application is a continuation-in-part of U.S. Ser. No. 10/105,775, filed Mar. 21, 2002, which is a continuation-in-part of U.S. Ser. No. 09/479,781 filed Jan. 7, 2000 (Attorney Docket No, KROL0003) and which claims priority to U.S. Ser. No. 60/278,557 filed Mar. 23, 2001, each of which is incorporated herein in its entirety by this reference thereto.

[0002] 1. Technical Field

[0003] The invention relates to network security. More particularly, the invention relates to a system and method based on a core of network objects for representing network security policy at a high level of abstraction so as to provide a simplified and natural way of creating and maintaining a network security policy.

[0004] 2. Description of the Prior Art

[0005] Security administrators need tools that help them formulate their site security policy and translate it into monitoring and enforcement mechanisms. They need to be sure that the computer enforced policy—often cobbled together from a plethora of disjoint access control mechanisms—matches their enterprise policy, all too often specified in a loose natural language or a set of unwritten principles. This leads to confusion as to why access is being granted or denied to particular resources and may lead to unintentional breaches of security.

[0006] A way to reduce or eliminate the confusion described above is by providing a user-friendly and, yet, rigorous way of specifying security policy, as well as providing tools for monitoring and enforcing the security policy.

[0007] Blaze, Feigenbaum, and Lacy (BFL), Decentralized Trust Management, Proc. IEEE Conference on Security and Privacy (1996), used the term trust management to refer to a problem of deciding whether requested actions, supported by credentials, conform to policies. In other words, it deals with the questions of who, how, and what. Who (the principals, for example, people, computers and organizations) can access what (the resources being sought) and how (the actions performed against the target resources).

[0008] Mansouri-Samani, et al, GEM: A Generalized Monitoring Language for Distributed Systems, Distributed Systems Engineering, vol.4, no. 2 96-108 (June 1997) discloses a generalized-event monitoring notation that permits user-specified filtering and composition scripts to be dynamically loaded into distributed-event monitoring components. GEM uses “scheduled time events and default or user-defined detection windows” to cope with “variable communication delay problems.” The GEM event monitoring system is used “to detect complex event sequences and to convert these into simple events” that trigger management actions. The event monitors have been restricted to performing “very simple activities related to triggering or notifying events.”

[0009] J. A. Grompone, A Declarative Language for the Configuration of Exchanges, Telecommunications Journal, vol. 56, no. 1 (January 1989) discloses the design and implementation of a high-level language, LEP, to define the routing and customizing of rules of a telex exchange. The routing concepts are basic and few in number. Each of the physical communication paths is called a line. The lines are arranged in groups. The purpose of the LEP language is to provide a comprehensive definition of all lines of an exchange, the arrangement of these lines in groups and the physical attributes of the groups. All groups taken together comprise all the lines without any lines missing or being repeated. A group is an ordered set of lines. The LEP term “access” is used to denote whether lines are permitted or forbidden to access other lines or services. Routing, a basic objective of an LEP program, is a way of associating sets of compiled codes with destinations, done through a sequence of elementary declarations. LEP also defines the possible destinations of a call. One of the main design concepts was to use a very simple structure for the declarations for even users unfamiliar with computer programming.

[0010] The LEP language cannot thread together multiple protocol layers of a network event. The LEP language lacks the sophistication in terms of richer expressions to allow a set of policy rules affecting different networking protocols to be applied to a complex protocol interaction between two communicating parties, and to security policy for an entire network. The LEP language does not suggest defining allowed traffic patterns and handling those events that deviate from those patterns.

[0011] Plasek, et al, Statistical Database Query Using Random Sampling Of Records, U.S. Pat. No. 5,878,426, discloses a method for obtaining decision support query results from a database table having multiple records. An attribute of the database table is sampled, which results in a collection of sampled data. The sampled data represents some percentage of all of the data corresponding to that attribute in the database table. The data associated with the attribute includes multiple data classes, and the sampled data is separated or partitioned into these data classes. A database query is applied to the sampled data rather than to all of the data corresponding to that attribute in the database table.

[0012] Plasek, et al, also discloses a method to obtain decision support query results from a database table where all of the data associated with a particular database attribute is grouped into various data classes. Each of the data classes is individually randomly sampled to obtain a corresponding number of class data samples. Each of the class data samples is then queried, which can include executing aggregation functions on each of the class data samples.

[0013] Plasek, et al, also discloses a method for providing result approximations in database queries.

[0014] Plasek, et al, does not disclose nor suggest providing a method to select a most specific and applicable result or policy rule. Plasek, et al, does not disclose nor suggest providing a method to rank data and does not order data in a database beyond partitioning data into classes and thereafter randomly sampling each data class such that database queries are applied to each of the samples.

[0015] Plasek, et al, does not disclose nor suggest providing a method to thread protocol layers of a network event together to provide a result to the network event.

[0016] Chow, et al, System, Method, and Program for Extending a SQL Compiler for Handling Control Statements Packaged with SQL Query Statements, U.S. Pat. No. 5,875,334 (Feb. 23, 1999) discloses an integrated compiler for compiling SQL3 control statements having procedural, i.e., control, information packaged together with query, i.e., non-procedural, statements. A query extractor contained within the parser extracts the query statement from the control statement leaving a control skeleton. The query statement is processed as usual through a query compiler for generating executable plans with the exception that the name resolution function for resolving variables is modified for looking up local variables. This modification takes into account the mapping of local and host variables to create a unification of local and host variables. The control skeleton is processed through a control analyzer which generates a representation of the control flow and a scope and symbol table. The control analyzer also unifies the local and host variables. A plan synthesizer then takes as input the control flow information, symbol tables, and individual executable plans for the query statements and generates a meta-plan comprising a merger of a top level plan for the control skeleton and sub-plans representing the executable plans of the query statement.

[0017] Chow, et al, does not disclose nor suggest a ranking method or an ordering method to handle a set of rules to be applied to a complex protocol interaction between two communicating parties.

[0018] Nor does Chow, et al, disclose or suggest a method whereby to thread protocol layers of a network event together to provide a rule applicable to the network event.

[0019] V. Paxson, Bro: A System for Detecting Network Intruders in Real-Time, Network Research Group, Lawrence Berkeley National Laboratory, Berkeley, Calif., LBNL-41197 (January 1998) discloses a stand-alone system for detecting network intruders in real-time by passively monitoring a network link over which the intruder's traffic transits. The system comprises a “policy script interpreter” that interprets event handlers written in a specialized language used to express a site's security policy. The specialized language is C-style because it comprises, for example, C-style data types and constants, operators, and block statements and is procedural. Bro comprises first-class values and aggregate types such as record and table, used to specify a security policy.

[0020] However, Paxson does not disclose nor suggest providing a sophisticated ranking, method to rank policy rules according to the specificity of the initiator and target communicating hosts and to select a most applicable rule in an efficient manner. Paxson does not disclose nor suggest providing a method to thread protocol layers of a network event together to provide a result to the entire network event.

[0021] It would be advantageous to reduce or eliminate the confusion described herein above by providing a user-friendly and, yet, rigorous way of specifying security policy, as well as providing tools for monitoring and enforcing the security policy.

[0022] It would be advantageous to have a trust manager that takes as its input a security policy defined as a set of policy rules (statements about trust) and a set of credentials (statements about principals), such that it is capable of processing requests for trust decisions, i.e. evaluating compliance with the policy.

[0023] It would be advantageous to provide a system and method for managing and continuously improving the security of complex networks, to specify formally the business practices and security policies governing their network operation, to evaluate network traffic against the policy specification providing actionable information to mitigate security risk and improve network operation.

[0024] A policy developer studio comprising: a meta-policy core of network objects, a policy developer graphical user interface (GUI) tool for providing a front end to a policy language, an output in XML, a compiled output for a policy engine, and an output in human readable form is provided.

[0051] A policy developer studio comprising: a meta-policy core of network objects, a policy developer graphical user interface (GUI) tool for providing a front end to a policy language, an output in XML, a compiled output for a policy engine, and an output in human readable form is provided and is discussed in detail in the section entitled, An Exemplary Policy Developer System, herein below.

[0052] Overview

[0053] FIG. 1 is a schematic diagram showing the relationship of elements of the Policy Monitoring System 100, according to the preferred embodiment of the invention. To effect a security policy decision, a policy manager module invokes a Policy Engine 101 with both a reference to a pre-defined security policy and a number of inputs it received from an Agent 102. These inputs describe a protocol event such as a TCP connection, an SSL session, or an HTTP GET. The end to end interaction between two communicating entities comprises one or more protocol events and it is termed a network event 103. For example, the retrieval of a web page from a web server by a web browser is a network event that typically consists of an IP protocol event, a TCP protocol event and an HTTP protocol event.

[0054] In the preferred embodiment the Policy Engine 101 consults a policy information database, a Policy Store 104 to determine a policy rule that applies to the network event 103. In the preferred embodiment the Policy Engine 101 collects input from the Agent 102 about each protocol event until it has enough information to consult the Policy Store 104. Once an applicable policy rule for the entire network event 103 has been found, the Policy Engine 101 returns a disposition 105 for the event to the policy manager module which in turn forwards it to the Agent 102, to a logging subsystem and, optionally, to an enforcement subsystem.

[0055] A definition of a protocol event is provided to facilitate understanding of the invention. A protocol event 120 as shown in FIG. 2 comprises the following elements:

[0056] 1) The Principals. Every policy decision involves two principals: an initiator 121 (an active principal) and a target 122 (a passive principal). Principals are identified by a set of one or more credentials, depending on how much information is known about them and what protocol service they are using. There are three types of credentials:

• • [0057] a) Host credentials. These are the physical network address, i.e. a MAC address, and the network attachment point, e.g. an IP address and port number.
  • [0058] b) User credentials. These may be weak credentials, e.g. a user name and password, or strong credentials, e.g. an X.509 certificate.
  • [0059] c) Object credentials. These identify a resource or an application, e.g. a URL or a pathname.

[0060] 2) The Protocol. The protocol service 123 associated with this protocol event 120.

[0061] 3) The Security Quality of Service Parameters. Some protocols include security QOS parameters 124 and these may be subject to local security policy constraints. For example, in the SSL protocol the ciphersuite negotiated between the SSL client and the. SSL server is a security QOS parameter.

[0062] 4) The Action. Every interaction between an initiator and a target over a given protocol service involves a specific action 125. Clearly, not all actions are of interest to the policy manager module. For example, in the SSL protocol only actions pertaining to the establishment or termination of an SSL session, most notably, the negotiation of security parameters for the session are of interest. In the LDAP protocol, on the other hand, a security policy administrator may wish to express policy statements about different LDAP data manipulation operations, such as, the SEARCH and MODIFY operations.

[0063] In one embodiment of the invention, while processing a network event 103, and before issuing a final ruling, the Policy Engine 101 may instruct the Agent 102 to carry out specific actions against the network event 103. For example, the. Agent 102 may be asked to decrypt subsequent SSL traffic or it may be asked to impose a specific ciphersuite on the target system. These instructions constitute an intermediate output of the Policy Engine 101 and are issued in the form of agent directives, defined herein below.

[0064] Once the Policy Engine 101 arrives at a final policy decision, it produces a disposition 105 for the event 103. The disposition 105 as shown in FIG. 3 comprises the following elements:

[0065] 1) Disposition Code. The disposition code 131 denotes whether or not the event 103 complies with the security policy and, if not, identifies the specific policy violation. A list of possible codes in a preferred embodiment is given in Table A herein below. This field is mandatory.

[0066] 2) Logging Directives. The logging directives field 132 includes a severity code, denoting the severity of the policy violation. A list of possible severity values in a preferred embodiment is given herein below in Table B. The severity code may be used by a logging subsystem to filter the event 103 and its disposition 105 or to control a notification action, e.g. page a network operator. In another embodiment the logging directives 132 may also include an optional human readable description summarizing the specific policy that determined the final disposition 105 e.g. “blue users cannot access the red server”. The logging directives field 132 is mandatory if the disposition code 131 indicates a policy violation.

[0067] 3) Agent Directives. Agent directives 102 are any instructions that need to be communicated to the Agent 102 and in another embodiment to more than one Agent. For example, the Agent 133 may be instructed to log all traffic associated with the event 103 or to disrupt communications between the initiator 121 and the target 122. In some embodiments, an Agent 102 only supports monitoring functions, or only enforcement functions, or be limited in its support of other types of functions. In a preferred embodiment, a policy manager is responsible for distributing a set of directives to appropriate Agents.

[0068] 4) Event Constraints. Event constraints 134 are any constraints to be applied to the event 103. For example, in one embodiment these constraints are protocol-specific constraints such as the maximum lifetime of a TCP connection or the maximum lifetime of an SSL session. In another embodiment, these constraints are communicated to the Agent reporting the event or simply to a policy manager.

TABLE A
Built-in Objects
The following is a set of built-in language objects known to both the
policy compiler and the policy engine.
First the built-in groups. It should be noted that, unlike user-defined
groups, built-in groups cannot be extended in a policy specification.
// List of supported protocols
( group all-protocols protocol_t
( union IP UDP ICMP TCP SSL HTTP )
// NOTE: new protocols can be added as needed
)
// List of supported hash algorithms
( group hash-algorithms hash_alg_t
( union MD5 SHA1 )
)
// List of supported agent directives
( group agent-directives agent_directive_t
( union DECRYPT DISRUPT LOG_TRAFFIC )
)
// List of supported logging severity codes
( group severity-codes severity_t
( union CRITICAL HIGH MEDIUM WARNING MONITOR
INFORMATION )
)
// List of supported disposition codes
( group disposition-codes code_t
( union OK CONTINUE ACCESS_DENIED
AUTHENTICATION_VIOLATION
SECURITY_ATTACK
SECURITY_QOS POLICY_ERROR )
)
// Certificate status values for valid certificates
( group valid-certs cert_status_t
( union VALID )
)
// Certificate status values for certificates rendered invalid
( group invalid-certs cert_status_t
( union EXPIRED NOT_YET_VALID REVOKED SUSPENDED )
)
// Certificate status values for rejected certificates
( group rejected-certs cert_status_t
( union MALFORMED
UNSUPPORTED_CRITICAL_EXTENSION )
)
// Certificate status values for all bad certificates
( group bad-certs cert_status_t
( union rejected-certs invalid-certs )
)
// List of all possible certificate status values
( group cert-status-values cert_status_t
( union valid-certs invalid-certs rejected-certs )
)
// List of all possible authentication status values
( group auth-status-values auth_status_t
( union SUCCEEDED REJECTED ABORTED )
)
// List of all SSL ciphersuites
( group ssl-ciphersuites ciphersuite_t
( union SSL_RSA_WITH_NULL_MD5
SSL_RSA_WITH_NULL_SHA
SSL_RSA_EXPORT_WITH_RC4_40_MD5
SSL_RSA_EXPORT_WITH_RC2_CBC_40_MD5
SSL_RSA_EXPORT_WITH_DES40_CBC_SHA
SSL_RSA_WITH_RC4_128_MD5
SSL_RSA_WITH_RC4_128_SHA
SSL_RSA_WITH_IDEA_CBC_SHA
SSL_RSA_WITH_DES_CBC_SHA
SSL_RSA_WITH_3DES_EDE_CBC_SHA
SSL_DH_RSA_WITH_3DES_EDE_CBC_SHA
SSL_DH_DSS_WITH_3DES_EDE_CBC_SHA
SSL_DH_RSA_WITH_DES_CBC_SHA
SSL_DH_DSS_WITH_DES_CBC_SHA
SSL_DH_RSA_EXPORT_WITH_DES40_CBC_SHA
SSL_DH_DSS_EXPORT_WITH_DES40_CBC_SHA
SSL_DH_ANON_EXPORT_WITH_RC4_40_MD5
SSL_DH_ANON_WITH_RC4_128_MD5
SSL_DH_ANON_EXPORT_WITH_DES40_CBC_SHA
SSL_DH_ANON_WITH_DES_CBC_SHA
SSL_DH_ANON_WITH_3DES_EDE_CBC_SHA
SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA
SSL_DHE_DSS_WITH_3DES_EDE_CBC_SHA
SSL_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA
SSL_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA
SSL_DHE_RSA_WITH_DES_CBC_SHA
SSL_DHE_DSS_WITH_DES_CBC_SHA
SSL_FORTEZZA_KEA_WITH_NULL_SHA
SSL_FORTEZZA_KEA_WITH_FORTEZZA_CBC_SHA
SSL_FORTEZZA_KEA_WITH_RC4_128_SHA
SSL_V2_RC4_128_WITH_MD5
SSL_V2_RC4_128_EXPORT40_WITH_MD5
SSL_V2_RC2_CBC_128_CBC_WITH_MD5
SSL_V2_RC2_CBC_128_CBC_EXPORT40_WITH_MD5
SSL_V2_IDEA_128_CBC_WITH_MD5
SSL_V2_DES_64_CBC_WITH_MD5
SSL_V2_DES_192_EDE3_CBC_WITH_MD5
)
)
// List of supported action codes for TCP
( group tcp-action-codes action_t
( union CONNECT
MISSED_CONNECT
TIMEOUT
ABORT
CLOSE )
)
// List of supported action codes for UDP
( group udp-action-codes action_t
ASSOCIATION
)
// List of supported action codes for IP
( group ip-action-codes action_t
ASSOCIATION
)
// List of supported action codes for ICMP
( group icmp-action-codes action_t
( union ASSOCIATION
BAD_CODE
FRAGMENTATION_NEEDED
HOST_UNREACHABLE
NETWORK_UNREACHABLE
PORT_UNREACHABLE
PROTOCOL_UNREACHABLE
SOURCE_ROUTE_FAILED
ECHO
ECHO_REPLY
INFORMATION_REQUEST
INFORMATION_REPLY
PARAMETER_PROBLEM
REDIRECT_HOST
REDIRECT_TYPE_OF_SERVICE_AND_HOST
REDIRECT_NETWORK
REDIRECT_TYPE_OF_SERVICE_AND_NETWORK
SOURCE_QUENCH
TIME_TO_LIVE_EXCEEDED
REASSEMBLY_TIME_EXCEEDED
TIMESTAMP
TIMESTAMP_REPLY )
)
// List of supported action codes for SSL
( group ssl-action-codes action_t
( union HANDSHAKE
MISSED_HANDSHAKE
SESSION_CLOSED
SESSION_ABORTED )
)
// List of supported action codes for HTTP
( group http-action-codes action_t
( union GET
HEAD
POST
PUT
DELETE
OPTIONS
TRACE
CONNECT
MISSED_REQUEST
RESPONSE )
)
// List of all supported action codes
( group all-action-codes action_t
( union udp-action-codes
ip-action-codes
icmp-action-codes
tcp-action-codes
ssl-action-codes
http-action-codes )
)

[0069] Now, the dispositions and policy rules built into the Policy Engine. These rules can be overwritten by user-defined policy rules.

	( disposition ok
	( code OK )
	)
	( disposition continue
	( code CONTINUE )
	)
	( disposition policy-error
	( description   “Policy error caused by uncaught event” )
	( code POLICY_ERROR )
	( log-directive
	CRITICAL
	“Uncaught event” )
	)
	( rule default-rule
	( description   “Catch-all rule for all protocols” )
	( protocol present )
	( action present )
	( initiator ignore )
	( target ignore )
	( outcome
	( final
	( default policy-error )
	)
	)
	)

[0070] It is noted that the list of built-in objects included in Table A is by no means complete. In other embodiments, the set of built-in objects is expanded or reduced to reflect the set of protocols supported by the Policy Monitoring System.

[0071] It is noted that in the preferred embodiment the Policy Engine 101 ranks default-rule lower than any user-defined rule. For example, a user-defined rule having initiator and target credentials set to ignore ranks higher than using default-rule.

[0072] In a preferred embodiment, security policy decisions are also affected by any previous history of security violations involving one or both of the principals. FIG. 4 is a schematic diagram of communicating parties according to the invention; wherein an initiator host machine 141 attempts to contact a target host machine 142 over a network, and its events are listened to by an Agent 102 and events are passed onto the invention herein 100. For example, a host machine 141 that repeatedly attempts to perform an illegal operation within a given time window may be blacklisted and rendered incapable of conducting further communication activity within the security domain. In one embodiment, a policy manager maintains a count of security policy violations perpetrated by or against specific principals and provides that information to the Policy Engine 101 as input to a policy evaluation procedure.

[0073] Specification Language

[0074] A security policy is formulated using the Policy manager module's policy specification language (FIG. 1) 108. A preferred embodiment chooses a simplified form of S-expressions as the policy specification language 108. S-expressions are LISP-like parenthesized expressions. The preferred embodiment uses a variant of S-expressions devised by Ron Rivest in R. Rivest, code and description of S-expressions, http://theory.les.mit.edu/˜rivest/sexp.html, and used in SPKI/SDSI in

[0075] C. Ellison, SPKI Certificate Documentation, http://www.clark.net/pub/cme/html/spki.html. In the preferred embodiment the use of Rivest's S-expressions are restricted in a way such that no empty lists are allowed and such that each list must have a type (a byte string) as its first element, denoting the type of the object represented by the list. The use of Rivest's S-expressions is further restricted by only requiring support for the canonical and advanced representations of S-expressions, a preferred embodiment of which is depicted in Table B herein below.

[0076] An advantage of using the canonical representation of S-expressions in the preferred embodiment is for digital signature purposes as well as for relatively efficient communication. It is easy to parse, fairly compact, and is unique for any given S-expression. An advantage of using the advanced representation of S-expressions is for human consumption. It can be thought of as a pretty print of the canonical representation.

	TABLE B
	An example of an advanced representation:
	( certificate ( issuer alice ) ( subject bob ) )
	An example of a canonical representation:
	(11:certificate(6:issuer5:alice)(7:subject3:bob))

[0077] It should be noted that replacing language tokens (e.g. certificate, issuer) with minimally encoded identifiers further optimizes the canonical representation.

[0078] The main advantages of using S-expressions in the preferred embodiment are:

• • [0079] It is easy to represent arbitrary data with S-expressions.
  • [0080] S-expressions are easy to extend and modify.
  • [0081] In their advanced representation they are easy to read and edit using, for example, a simple text editor.
  • [0082] Their canonical representation was designed for efficient packing and parsing. In particular, parsing requires minimal look-ahead and no re-scanning.
  • [0083] Their canonical representation allows for easy transportation, for example, in files or email messages.
  • [0084] In their canonical encoding they can be digitally signed.
  • [0085] It is relatively simple to convert between the advanced and the canonical representation of S-expressions.

[0086] A formal description of the policy specification language 108 is provided herein below in Table C.

TABLE C
This table contains a Backus-Naur Form (BNF) description of the
grammar for the policy specification language, including an
annotation section. All valid policies derive from the <policy> production.
This grammar applies to the policy specification after all comments are
removed and all macros are expanded. Comments begin with “//” and
extend to the end-of-line. Macros are defined using the C macro syntax.
Incomplete parts of the grammar are noted in italics. Terminals are shown
in bold.
//
// Basic language stuff
//
// Terminals requiring further syntax specification
<integer> ::= TBD	// [0-9]*
<symbol> ::= TBD	// alphanumeric and ‘-‘,
	// ‘_’, starts with letter
<string> ::= <concat> | TBD // any ASCII character
	// enclosed in double-quotes
<mac-addr> ::= TBD	// 6 hex byte values
	// separated by ‘-‘
<ip-addr> ::= TBD	// IPv4 dotted decimal
	// notation
<ip-mask> ::= TBD	// address prefix per
	// RFC-2280
<hex-string> ::= TBD	// n hex byte values
	// separated by ‘:’
<version-string> ::= TBD	// a string of the form
	// <major>.<minor>
// Some productions used only for clarity
<name> ::= <symbol>
<type> ::= <symbol>
<attr-name> ::= <symbol>
// The basic types in the language
<atom> ::= <symbol> | <integer> | <string> |
<ip-addr> | <mac-addr> |
<version> | <hash-atom> | <bool>
//
// Productions for the policy specification section
//
// These are values that describe the values of things with values
<meta-value> ::= present | absent | ignore
// Productions used in a few places
<assertion> ::= ( assertion <bool-expr> )
// Version conversion function
<version> ::= ( version <version-string> )
// Attributes, used as arguments in predicates and other operations
<attr-part-list> ::= <atom> |
<attr-part-list> <atom>
<attr-op> ::= ( <attr-name> <attr-part-list> )
<attribute> ::= <attr-name> | <attr-op>
// Hashes
<hash-alg-name> ::= [Some set of terminals of type hash_alg_t]
<hash-op> ::= ( hash <hash-alg-name> <attribute> )
<hash-atom> ::= <hex-string>
<hash> ::= <hash-atom> | <hash-op>
// Operations that operate on attributes and return a
// basic type (atom)
<atom-ops> ::= <hash-op>
// Predicates - used in building boolean expressions
<generic-compare-op> ::= eq
<num-compare-op> ::= gt | lt | ge | le
<rng-compare-op> ::= range
<string-compare-op> ::= prefix | substring
<member-compare-op> ::= member
<ipmask-compare-op> ::= ip-mask
<iprng-compare-op> ::= ip-range
<cred-match-op> ::= root | has
<presence-op> ::= present | absent
// Generic argument
<arg> ::= <attribute> | <atom> | <atom-ops>
<generic-cmp-arg> ::= <arg>
<generic-compare> ::= ( <generic-compare-op>
<generic-cmp-arg> <generic-cmp-arg> )
<num-cmp-arg> ::= <attribute> | <integer> | <version>
<num-compare> ::= ( <num-compare-op>
<num-cmp-arg> <num-cmp-arg> ) |
( <rng-compare-op>
<num-cmp-arg>
<num-cmp-arg> <num-cmp-arg> )
<string-cmp-arg> ::= <attribute> | <string>
<string-compare> ::= ( <string-compare-op>
<string-cmp-arg> <string-cmp-arg> )
<member-cmp-arg> ::= <arg>
<member-part-list> ::= <member-cmp-arg> <union> |
<member-cmp-arg> <member-cmp-arg>
<member-compare> ::= ( <member-compare-op>
<member-part-list> )
<ipmask-compare> ::= ( <ipmask-compare-op>
<attribute> <ip-mask> )
<iprng-cmp-arg> ::= <attribute> | <ip-addr>
<iprng-compare> ::= ( <iprng-compare-op>
<iprng-cmp-arg>
<iprng-cmp-arg> <iprng-cmp-arg> )
<cred-match> ::= ( <cred-match-op> <attribute> <cred-name> )
<presence> ::= ( <presence-op> <attribute> )
<predicate> ::= <generic-compare> | <num-compare> |
<string-compare> | <member-compare> |
<ipmask-compare> | <iprng-compare> |
<cred-match> | <presence>
// Boolean expressions
<bool-list-op> ::= and | or
<bool-monadic-op> ::= not
<bool> ::= TRUE | FALSE
<bool-list> ::= <bool-expr> | <bool-list> <bool-expr>
<bool-expr> ::= <name> | <bool> | <predicate> |
( <bool-monadic-op> <bool-expr> ) |
( <bool-list-op> <bool-list> )
// Descriptions are comments that are carried along with the constructs
<string-list> ::= <string> | <string-list> <string>
<description> ::= ( description <string-list> )
// When we need to break up a string across lines, we use concat to
// put it back together (just like descriptions)
<concat> ::= ( concat <string-list> )
// Unions are unnamed collections of one or more symbols
// (with matching types)
<union-symbol> ::= <atom> | <group-name>
<union-list> ::= <union-symbol> |
<union-list> <union-symbol> |
( union <union-list> ) |
<union-list> ( union <union-list> )
<union> ::= ( union <union-list> ) | <union-symbol>
// Groups are named and typed unions (all symbols must have one type)
<group-part-list> ::= <union> | <description> <union> |
<union> <description>
<group-name> ::= <name>
<group> ::= ( group <group-name> <type>
<group-part-list> )
// Credentials
<cred-part> ::= <description> | <assertion>
<cred-part-list> ::= <cred-part> | <cred-part-list> <cred-part>
<cred-name> ::= <name>
<credential> ::= ( credential <cred-name>
<cred-part-list> )
// Dispositions
<agent-directives> ::= [Some set of terminals of type
agent_directive_t]
<agent-directive-list> ::= <agent-directives> |
<agent-directive-list> <agent-directives>
<agent-directive> ::= ( agent-directive <agent-directive-list> )
// preliminary list of severity codes; more TBD
<log-severity> ::= [Some set of terminals of type severity_t]
<log-directive> ::= ( log-directive <log-severity> <string> ) |
( log-directive <log-severity> )
// preliminary list of disposition codes; more TBD
<disposition-code> ::= [Some set of terminals of type code_t]
<disp-code> ::= ( code <disposition-code> )
<disp-part> ::= <description> | <disp-code> |
<log-directive> | <agent-directive>
<disp-part-list> ::= <disp-part> | <disp-part-list> <disp-part>
<disposition-name> ::= <name>
<disposition> ::= ( disposition <disposition-name>
<disp-part-list> )
// Conditions
<condition-part-list> ::= <description> <assertion> |
<assertion> <description> |
<assertion>
<condition-name> ::= <name>
<condition> ::= ( condition <condition-name>
<condition-part-list> )
// Outcomes are bindings of conditions to dispositions used in rules
<outcome-default> ::= ( default <disposition-name> )
<guard> ::= if | ifnot
<outcome-clause> ::= ( <guard> <condition-name>
<disposition-name> )
<outcome-list> ::= <outcome-default> |
<outcome-clause> <outcome-list>
<immediate> ::= ( immediate <outcome-list> )
<final> ::= ( final <outcome-list> )
<outcome-types> ::= <immediate> | <final> |
<immediate> <final> |
<final> <immediate>
<outcome> ::= ( outcome <outcome-types> )
// Rules
<protocol> ::= ( protocol <union> ) |
( protocol <meta-value> )
<action> ::= ( action <union> ) |
( action <meta-value> )
<initiator> ::= ( initiator <cred-name> ) |
( initiator <meta-value> )
<target> ::= ( target <cred-name> ) |
( target <meta-value> )
<agent> ::= ( agent <cred-name> )
<rule-name> ::= <name>
<rule-list> ::= <rule-name> | <rule-list> <rule-name>
<prerequisite> ::= ( prerequisite <rule-list> )
<rank-above> ::= ( rank-above <rule-name> )
<rule-part> ::= <description> | <protocol> | <action> |
<initiator> | <target> | <outcome> |
<prerequisite> | <rank-above> | <agent>
<rule-part-list> ::= <rule-part> | <rule-part-list> <rule-part>
<rule> ::= ( rule <rule-name>
<rule-part-list> )
// Policy is the top-level construct of the policy
// specification section
<policy-part> ::= <description> | <group> | <credential> |
<condition> | <disposition> | <rule>
<policy-part-list> ::= <policy-part> |
<policy-part-list> <policy-part>
<policy-name> ::= <name>
<language-version> ::= <version-string>
<policy> ::= ( policy <policy-name> <language-version>
<policy-part-list> )
//
// Productions for the annotation section
//
<assertion-type> ::= <meta-value> | single-value | multi-value
<weight> ::= ( weight <symbol> <assertion-type> )
<weight-penalty> ::= ( weight-penalty <integer> )
<rank-cred-part> ::= <weight> | <weight-penalty>
<rank-cred-part-list> ::= <rank-cred-part> |
<rank-cred-part-list> <rank-cred-part>
<ranked-credential> ::= ( ranked-credential <cred-name>
<rank-cred-part-list>
// Annotation is the top-level construct of the annotation section
<annotation-part-list> ::= <ranked-credential> |
<annotation-part-list> <ranked-credential>
<annotation> ::= ( annotation <policy-name>
<language-version>
<annotation-part-list> )

[0087] In the preferred embodiment the policy specification language 108 is typed. The policy compiler 101 performs the necessary type checking of all S-expressions found in a policy specification 107. Typing aids in catching and diagnosing both common and subtle user errors. A preferred embodiment of the type information is described herein below in Table D.

TABLE D
Types
The subtables in this section describe, in a pseudo-formal manner, the type
information in the language that is enforced by the parser. The types used
should be self-evident.
First some notation used throughout the tables:
( list-of type ) - ( foo ( list-of T ) ) → ( foo A B C ) where A, B, and C are
of the type T; the list must have at least one element.
( multi-of type ) - ( foo ( multi-of T ) ) → ( foo ( union A B C ) ) where
A, B, and C are of the type T or → ( foo ABC ) where ABC is the name
of a group of type T.
( mix-of type1 type2 type3 ) - ( foo ( mix-of R S T ) ) → ( foo A B C D )
where A, B, C, and D are randomly of types R, S, and T.
match - a type that is required to be the same as all other occurrences of
match in the expression -
( foo match match ) requires that the two arguments of foo be of the
same type (e.g., int_t, string_t).

[0088] The following table lists the typed attributes used in conditions and credentials.

	Applicable	Argument
Attribute Name	Protocols	Types	Result Type
agent-attribute	all-protocols	—	(multi-of
			agent_attr_t)
auth-status	SSL		auth_status_t
cert-status	SSL	—	cert_status_t
der-cert	SSL	—	octet_string_t
encipher-keysize	SSL	—	int_t
http-cookie	HTTP	string_t	(multi-of
			string_t)
http-password	HTTP	—	string_t
http-req-hdr	HTTP	string_t	string_t
http-resp-hdr	HTTP	string_t	string_t
http-set-cookie	HTTP	string_t	(multi-of
			string_t)
http-status-code	HTTP	—	int_t
http-username	HTTP	—	string_t
icmp-gateway-	ICMP	—	ip_addr_t
address
icmp-nested-address	ICMP	—	ip_addr_t
icmp-nested-port	ICMP	—	int_t
initiator-access-rate	all-protocols	—	int_t
initiator-auth-keysize	SSL	—	int_t
initiator-violation-rate	all-protocols	—	int_t
ip-address	IP UDP TCP ICMP	—	ip_addr_t
ip-port	IP UDP TCP ICMP	—	int_t
ke-keysize	SSL	—	int_t
mac-address	IP UDP TCP ICMP	—	mac_addr_t
protocol-version	all-protocols	—	version_t
ssl-ciphersuite	SSL	—	ciphersuite_t
target-access-rate	all-protocols	—	int_t
target-auth-keysize	SSL	—	int_t
target-violation-rate	all-protocols	—	int_t
url	HTTP	—	string_t
x509-cert-path	SSL	—	cert_path_t
x509-issuer	SSL	—	string_t
x509-subject	SSL	—	string_t

[0089] The table below lists all the operations in the language that return a dynamic result. For each operation it shows both argument and result types

	Operation	Result Type	Argument Types
	absent	bool_t	string_t
	and	bool_t	( list-of bool_t )
	default	disposition_t	disposition_t
	eq	bool_t	match match
	has	bool_t	cert_path_t cred_t
	hash	base64_t	hash_alg_t octet_string_t
	ge1	bool_t	match match
	gt1	bool_t	match match
	if	disposition_t	condition_t disposition_t
	ifnot	disposition_t	condition_t disposition_t
	ip-mask	bool_t	ip_addr_t ip_mask_t
	ip-range	bool_t	ip_addr_t ip_addr_t
			ip_addr_t
	le1	bool_t	match match
	lt1	bool_t	match match
	member	bool_t	match ( multi-of match )
	not	bool_t	bool_t
	or	bool_t	( list-of bool_t )
	prefix	bool_t	string_t string_t
	present	bool_t	string_t
	range1	bool_t	match match match
	root	bool_t	cert_path_t cred_t
	substring	bool_t	string_t string_t
	version	version_t	string_t
	1Operator only supports types int_t and version_t as arguments.

[0090] The table below is pushing the concept of “type” far beyond its normal meaning since, in it, we often use type merely to convey positional information. It shows the type of every object in the language and the types of their arguments.

Object Name	Object Type	“Argument” Types
action	act_t	( multi-of action_t )
agent	agt_t	credential_t
agent-	agtdir_t	( multi-of agent_directive_t )
directive
assertion	assert_t	bool_t
code	code_def_t	code_t
condition	cond_t	condition_t ( mix-of desc_t bool_t )
credential	cred_t	credential_t ( mix-of assert_t desc_t prot_t )
description	desc_t	( list-of string_t )
disposition	disp_t	disposition_t ( mix-of desc_t code_def_t log_t agtdir_t )
final	dispo_t	(list-of guard_t)
group	group_t	match type_t ( multi-of match )
immediate	dispo_t	(list-of guard_t)
initiator	init_t	credential_t
log-directive	log_t	severity_t string_t
outcome	out_t	( list-of dispo_t )
policy	policy_def_t	policy_t string_t ( mix-of desc_t group_t cred_t cond_t disp_t
		rule_def_t )
prerequisite	pre_t	( list-of rule_t )
protocol	prot_t	( multi-of protocol_t )
rank-above	rank_t	rule_t
rule	rule_def_t	rule_t ( mix-of desc_t agt_t prot_t act_t init_t targ_t out_t pre_t
		rank_t )
target	targ_t	credential_t
union	( multi-of match )	( list-of match )

[0091] It is noted that the list of credential and condition attributes included in Table D is by no means complete. In other embodiments, the set of attributes is expanded or reduced to reflect the set of protocols supported by the Policy Monitoring System.

[0092] It is noted that although the remainder of this disclosure describes the specification language 108 by means of examples, and that for improved readability, said examples use the advanced rather than the canonical representation of S-expressions, this is not meant to further limit the invention.

[0093] In the preferred embodiment of the invention, the language 108 allows for comments to be embedded in S-expressions. A comment is allowed anywhere whitespace is valid. A comment begins with “//” and continues to the end-of-line. In compilation, comments are ignored because they serve merely as an aid to the human user.

[0094] In the preferred embodiment of the invention, the language 108 allows for external files to be included using the #include syntax of C. Included files are supported to enhance modularity and reusability of policy language segments.

[0095] In the preferred embodiment of the invention, the language 108 allows for macros to be defined using the #define syntax of C. Macros are supported to enhance readability. By convention, macros start with an uppercase letter but need not be fully capitalized.

[0096] The language 108 comprises the following first-class objects:

• • [0097] Condition
  • [0098] Credential
  • [0099] Disposition
  • [0100] Group
  • [0101] Policy
  • [0102] Rule

[0103] In the preferred embodiment first-class objects have names. Names are normally used to refer to an object from another object. By convention, names of built-in objects start with a lowercase letter and use hyphens (-) to separate words. Names of user-defined objects start with an uppercase letter and use intercaps or underscores (_) to separate words, but do not use hyphens. Names of data types start with a lowercase letter and end with an underscore followed by a lowercase Ψ (_t).

[0104] In the preferred embodiment a named object must be defined before its name can be used. The scope of a name is that of the entire policy specification as defined by the policy object.

[0105] In the preferred embodiment first-class objects may optionally include a description field. The description provides human readable text associated with the object. Unlike comments, description fields are preserved by the policy parser. When using the advanced representation, description strings may be split across several lines, using the C rules of string concatenation. That is, following the description token are one or more character strings, each enclosed in a set of double quotes.

[0106] Policy

[0107] In the preferred embodiment a policy is the top-most object defined by the specification language 108 and includes all other first-class objects. A policy manager may load several policies into its internal database. However, at any one point in time, only one active policy is in effect. That is the policy known to the Policy Engine 101. Following is an example of a policy object.

( policy Sample_Policy_1 “1.0”    // policy <name> <version>
( description “This is a policy specification description”
“that is continued on a second line” )
...
)

[0108] In the preferred embodiment a policy object has two mandatory parameters: name, which is used to reference the policy, and version number, which defines the version of the policy specification language 108. A policy's version number is used to check for compatibility between a policy specification and a policy compiler.

[0109] Groups and Unions

[0110] In the preferred embodiment groups are named collections of a given type. The union object creates the collection from a set of items. The group object gives the union a name and a type. Following is an example expressing a collection of colors:

	( group SomeColors color_t    // group <name> <type>
	( description “Some colors I like” )
	( union RED GREEN YELLOW )
	)

[0111] In the example, the object identifies RED, GREEN and YELLOW as items, i.e. symbols, of type color_t (a fictitious data type) collected in a set named SomeColors. By convention, symbols defined in unions are fully capitalized.

[0112] In the preferred embodiment once a symbol is identified as being of a certain type, it is transparently added to an unnamed set of items of that type. It may then be reused in other unions, groups or wherever an individual item of that type is valid. For example, a valid way to define another group is as follows:

	( group RedByAnyOtherName color_t
	( description “Red in different languages” )
	( union RED ROSSO ROUGE VERMELHO )
	)

[0113] However in the preferred embodiment the following group would not be allowed since RED would already have been tagged as being of type color_t.

( group AfewOfMyFavoriteThings thing_t
( union RED PASTA WINE )// ERROR! RED previously defined as
)                // having type color_t

[0114] In the preferred embodiment sets can be combined with other predefined sets. For example,

	( group MoreColors color_t
	( union
	SomeColors
	RedByAnyOtherName  // overlapping ok
	PURPLE BEIGE BURGUNDY
	)
	)

[0115] It is noted that RED overlaps both SomeColors and RedByAnyOtherName, which according to the invention is perfectly acceptable. The resulting set will include only one instance of the set item RED.

[0116] In the preferred embodiment unions are similar to the C enum type, with the added benefit that unions can be combined and extended without concern for conflicting item values.

[0117] In a preferred embodiment unions are used, but are not limited to, to define collections of items, such as, for example, IP addresses, MAC addresses, integers, version numbers and hash values. That is, unions can define any data item that has a primitive data type in the language. An example of a group of IP addresses is defined as:

	( group MyComputers ip_addr_t
	( union
	207.5.63.23    // desktop at work
	207.5.63.42    // laptop
	128.7.16.64    // home computer
	)
	)

[0118] In the preferred embodiment the type of the items in the union must agree with the type specified in the group.

[0119] In a preferred embodiment, groups are referenced from other first-class objects. For example, groups are typically used to define collections of protocol actions, SSL ciphersuites, and IP addresses. Note that wherever a group is allowed, the following are also valid:

• • [0120] A union object (essentially, an unnamed group) provided that any symbols used as elements in the union have already been given a type via a group definition.
  • [0121] A single collection item. This is equivalent to a union object with a single element. If the item is a symbol, its type must have been previously defined in a group.

[0122] A list of built-in groups is given in section Table A.

[0123] Credentials

[0124] In the preferred embodiment a credential is a statement about a principal in a protocol event. It consists of a logical expression containing one or more assertions about the attributes that make up a principal's credentials. When a policy rule is evaluated against a protocol event, the credentials presented in the protocol event are compared to the credentials specified in a purported credential object. If the logical expression defined in the credential object is satisfied, the principal's presented credentials are said to satisfy the purported credentials. As an example, the following purported credentials are satisfied if the principal's IP address is 207.5.63.8 and its IP port number is either 80 or greater than 443.

	( credential Credentials_Example_1    // credential <name>
	( assertion
	( and
	( eq ip-address 207.5.63.8 )
	( or
	( eq ip-port 80 )
	( gt ip-port 443 )
	)
	)
	)
	)

[0125] In the preferred embodiment each protocol has a set of attributes that may be used to build purported credentials. Table E herein below lists all the attributes currently defined and, for each attribute, it shows the protocols where the attribute might be included in the presented credentials, as well as the operations where the attribute may be used as an operand.

TABLE E
Attribute	Applicable
Name	Protocols	Description	Compare Operations
agent-	all-protocols2	The attributes of the reporting	member
attribute		Agent, as a union of symbolic
		names
cert-status	SSL	The validity status of a	eq, member
		certificate
der-cert	SSL	A DER encoded certificate	hash
http-	HTTP	The password used in basic	eq, member, substring,
password		authentication	prefix
http-	HTTP	The user name used in basic	eq, member, substring,
username		authentication	prefix
ip-address	IP UDP TCP ICMP	An IP address	eq, member, ip-mask,
			ip-range
ip-port	IP UDP TCP ICMP	An IP port	eq, member, gt, ge, lt,
			le, range
mac-address	IP UDP TCP ICMP	A MAC address	eq, member
url	HTTP	A URL	eq, member, substring,
			prefix
x509-cert-	SSL	An X.509 certificate chain	root, has
path
x509-issuer	SSL	An X.509 certificate issuer	eq, member, substring,
			prefix
x509-subject	SSL	An X.509 certificate subject	eq, member, substring,
			prefix
2Can be used to identify the reporting Agent in any policy rule but must not be mixed with other credential attributes.

[0126] It is noted that the list of credential attributes included in Table E is by no means complete. In other embodiments, the set of attributes is expanded or reduced to reflect the set of protocols supported by the Policy Monitoring System.

[0127] In the preferred embodiment each attribute can be thought of as having an implied getter function that returns its value. Most attribute getters take no arguments and return a single value. In the preferred embodiment, however, some attribute getters (e.g. http-req-hdr and http-cookie) are functions that take one or more arguments and may return complex results. For example, http-cookie takes as an argument the name of a cookie in an HTTP request header and returns its value or values as a union of strings.

[0128] In the preferred embodiment it is important not to mix credential attributes from different protocol sets in a credential specification. For example, combining ip-address and der-cert in the same credential object would be an error and flagged by the policy compiler. As another example, using a credential in a policy rule for a protocol action that is incompatible with the credential attributes in the credential object is considered an error, flagged by the policy compiler. However, it is possible to use those attributes in two separate credential objects and establish relationships between them within policy rules (e.g. access to resource X is restricted to principals previously authenticated with credentials Y). See example Check_Access_Denial herein below for an example of establishing this type of relationships in policy rules.

[0129] In the preferred embodiment the credential attribute agent-attribute is used to define the credentials of the Agent 102 reporting the protocol event 103. Agents are individually configured with a set of attributes, which are used to identify them to a policy manager. In another embodiment, some agent attributes might uniquely identify a specific Agent (e.g. MONITOR_NEXT_TO_ROUTER_X) while others might identify a group of Agents (e.g. ALL_MONITORS_IN_SUBNET_Y). The agent-attributes attribute returns a union of identification attributes for the reporting Agent 102. In the preferred embodiment within a credential specification, assertions about agent attributes may not be mixed with assertions about any other credential attributes.

[0130] Table F herein below lists all the operations used in a preferred embodiment to make assertions about attributes.

TABLE F
Operation	Description
absent	Whether (true) the attribute denoted by the operand does not have a value in the
	protocol event
and	Logical AND of a list of boolean expressions, its operands
eq	Whether (true) two operands have the same value
ge	Whether (true) the first operand's value is greater than, or equal to, the second's
gt	Whether (true) the first operand's value is greater than the second's
has	Whether (true) the certificate chain defined by the first operand's value contains a
	certificate that satisfies the second operand (a credential name)
hash	Computes a digest of the second operand's value using the hashing function
	defined by the first operand; returns the hash as a hexadecimal string
ip-mask	Whether (true) the first operand's value is included in the set of IP addresses
	defined by the second operand, an IP address prefix [RFC2280]; an address prefix
	is represented as an IPv4 address (dotted-decimal format with four integers)
	followed by the character slash “/” followed by an integer in the range from 0 to 32.
	The latter denotes the number of high-order bits from the preceding address that
	constitute a subnetwork address. If the subnetwork address bits match exactly the
	corresponding bits in the first operand's value, the operation returns true.
	The following are valid address prefixes: 128.9.128.5/32, 128.9.0.0/16, 0.0.0.0/0;
	the following address prefixes are invalid: 0/0, 128.9/16 since 0 or 128.9 are not
	dotted-decimal strings containing four integers.
ip-range	Whether (true) the first operand's value is included in the set of IPv4 addresses
	defined by an IP address range whose lower bound is the operand with the lower
	value and whose upper bound is the operand with the higher value; the three
	operand values are taken as 32-bit unsigned integers and, if the first operand value
	falls within the inclusive numerical range defined by the two other operand values,
	the operation returns true
le	Whether (true) the first operand's value is less than, or equal to, the second's
lt	Whether (true) the first operand's value is less than the second's
member	Whether (true) the first operand's value is a member of the set defined by the
	second operand (a union)
not	Logical negation of its operand's value
or	Logical OR of a list of boolean expressions, its operands
prefix	Whether (true) the string that constitutes the first operand's value includes, starting
	at the first character, the string defined by the second operand
present	Whether (true) the attribute denoted by the operand has a value in the protocol
	event
range	Whether (true) the first operand's value is within the inclusive numerical range
	defined by the values of the second a third operands; the range comprises the set
	of values between the lower operand value and the higher
root	Whether (true) the certificate chain defined by the first operand's value has, as its
	root, a certificate that satisfies the second operand (a credential name)
substring	Whether (true) the string that constitutes the first operand's value includes the string
	defined by the second operand

[0131] It is noted that the list of operations included in Table F is by no means complete. In other embodiments, the set of operations is expanded or reduced to reflect the set of protocols and features supported by the Policy Monitoring System.

[0132] In the preferred embodiment credentials may be combined with other credentials or with additional assertions. Consider the following example:

	( credential Credentials_Example_2
	( assertion
	( or
	Credentials_Example_1
	( and
	( ip-mask ip-address 207.5.0.0/16 )
	( range ip-port 25 443 )
	)
	)
	)
	)

[0133] The example herein above defines purported credentials that will be satisfied if either Credentials_Example_—1 is satisfied or if the presented credentials' IP address falls within the subnetwork defined by the address prefix 207.5.0.0/16 and if the IP port is between 25 and 443, inclusive.

[0134] In the preferred embodiment the absence of an assertion about a specific attribute in a credential specification indicates that its value is to be ignored in considering the presented credentials. In the preferred embodiment, it is often useful to indicate that a particular attribute must or must not be specified in the presented credentials, irrespective of the attribute's value, if any. The operations absent and present accomplish this, as illustrated by the following examples:

( credential Credentials_Example_3
( assertion
( and
// http-username must exist, but don't care about its value
( present http-username )
// the absence of an assertion about http-password indicates
// that its presence or absence is irrelevant
)
)
)
( credential Credentials_Example_4
( assertion
( and
// an X.509 certificate must not have been presented
( absent der-cert )
)
)
)

[0135] Conditions

[0136] In the preferred embodiment a condition defines a constraint upon a protocol event 103. Said condition comprises a logical expression containing one or more assertions about attributes of the protocol event. Policy rules use conditions to specify particular constraints that must or must not be satisfied by the protocol event 103.

[0137] Table G lists attributes of a protocol event 103 that may be used when formulating conditions. For each attribute the table shows protocols for which the attribute is defined, as well as the operations which can take the attribute as an operand.

TABLE G
Attribute	Applicable		Compare
Name	Protocols	Description	Operations
auth-status	SSL	The status of an authenticated session at the	eq, member
		end of the authentication handshake
encipher-	SSL	The size of the key used for data encipherment	eq, member,
keysize		(e.g., size of an IDEA key)	gt, ge, lt, le,
			range
http-cookie	HTTP	Takes as an argument the name of a cookie in	member
		the request header and returns its value(s) as
		a union of strings
http-req-hdr	HTTP	Takes as an argument the name of a client	eq, member,
		request header and returns its value	substring,
			prefix
http-resp-hdr	HTTP	Takes as an argument the name of a server	eq, member,
		response header and returns its value	substring,
			prefix
http-set-	HTTP	Takes as an argument the name of a cookie in	member
cookie		the response header and returns its value(s)
		as a union of strings
http-status-	HTTP	The status code returned on HTTP responses	eq, member,
code		(aka response code)	gt, ge, lt, le,
			range
icmp-	ICMP	The IP address of the gateway host on a	eq, member,
gateway-		redirect message	ip-mask, ip-
address			range
icmp-nested-	ICMP	The IP address carried in a ‘destination	eq, member,
address		unreachable’ message	ip-mask, ip-
			range
icmp-nested-	ICMP	The port number carried in a ‘destination	eq, member,
port		unreachable’ message	gt, ge, lt, le,
			range
initiator-	all-protocols	The rate at which the current active principal	eq, member,
access-rate		has been the initiator of communications, over	gt, ge, lt, le,
		a predefined (configurable) period of time	range
initiator-auth-	SSL	The size of the key used for initiator	eq, member,
keysize		authentication and/or digital signatures (e.g.,	gt, ge, lt, le,
		size of public key modulus)	range
initiator-	all-protocols	The rate at which the current active principal	eq, member,
violation-rate		has been the initiator of security policy	gt, ge, lt, le,
		violations, over a predefined (configurable)	range
		period of time
ke-keysize	SSL	The size of the key-encipherment key (e.g.,	eq, member,
		size of public key modulus)	gt, ge, lt, le,
			range
protocol-	all-protocols	The version of the protocol	eq, member,
version			gt, ge, lt, le,
			range
ssl-ciphersuite	SSL	The negotiated ciphersuite	eq, member
target-access-	all-protocols	The rate at which the current passive principal	eq, member,
rate		has been the target of communications, over a	gt, ge, lt, le,
		predefined (configurable) period of time	range
target-auth-	SSL	The size of the key used for target	eq, member,
keysize		authentication and/or digital signatures (e.g.,	gt, ge, lt, le,
		size of public key modulus)	range
target-	all-protocols	The rate at which the current passive principal	eq, member,
violation-rate		has been the target of security policy	gt, ge, lt, le,
		violations, over a predefined (configurable)	range
		period of time

[0138] It is noted that the list of condition attributes included in Table G is by no means complete. In other embodiments, the set of attributes is expanded or reduced to reflect the set of protocols and features supported by the Policy Monitoring System.

[0139] In the preferred embodiment operations listed in Table G may be used to build assertions about condition attributes.

[0140] In the preferred embodiment condition attributes cannot mix with those from different protocol sets in a condition specification. A condition used in a policy rule for a protocol that is incompatible with the condition attributes in the condition object is considered an error and is flagged by the policy compiler. For example, it is illegal to use ssl-ciphersuite in a condition referenced by a policy rule for HTTP.

[0141] Following are some examples:

( group Strong_RSA_Ciphersuites ciphersuite_t
( description  “Strong ciphers with RSA key exchange” )
( union SSL_RSA_WITH_RC4_128_MD5
SSL_RSA_WITH_RC4_128_SHA
SSL_RSA_WITH_IDEA_CBC_SHA
SSL_RSA_WITH_3DES_EDE_CBC_SHA
SSL_DH_RSA_WITH_3DES_EDE_CBC_SHA
SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA
)
)
( condition SslV3StrongCiphers    // condition <name>
( assertion
( and
( ge protocol-version ( version “3.0” ) )
( member ssl-ciphersuite Strong_RSA_Ciphersuites )
( ge ke-keysize 768 )
( ge target-auth-keysize 1024 )
)
)
)
( condition HackerTripwire
( assertion
( ge initiator-violation-rate 10 )
)
)
( condition ProtectSSL
( assertion
( and SslV3StrongCiphers HackerTripwire )
)
)

[0142] Herein above, the condition SsIV3StrongCiphers can be used with an SSL protocol event to ensure that SSL 3.0 or higher is used, that the negotiated ciphersuite is one of the strong RSA-based ciphersuites, that the RSA key-encipherment key has a modulus of no less than 768 bits, and that the RSA authentication key has a modulus of no less than 1024 bits.

[0143] Herein above, the condition HackerTripwire can be used with any protocol event 103 to ensure that the active principal 141 is not a potential attacker. The third condition, ProtectSSL, simply combines the first two.

[0144] Dispositions

[0145] In the preferred embodiment a disposition defines an outcome of a policy rule. Each policy rule may have many possible outcomes depending on, for example, constraints imposed on the protocol event.

[0146] See Table H herein for a list of disposition codes and an explanation of their meanings in the preferred embodiment.

TABLE H
Disposition Code	Description
OK	The network event conforms to the security
	policy
CONTINUE	Additional information is needed before
	determining whether or not the network event
	conforms to the security policy
ACCESS_DENIED	Access to the target resource is denied by the
	security policy
AUTHENTICATION_VIOLATION	Authentication between the communication
	parties does not conform to the requirements set
	out by the security policy
SECURITY_ATTACK	A security attack has been detected
SECURITY_QOS	The security quality of service parameters
	associated with a protocol event do not meet the
	requirements set out by the security policy
POLICY_ERROR	An error has been detected in the security policy
	specification

[0147] It is noted that the list of disposition codes included in Table H is by no means complete. In other embodiments, the set of disposition codes is expanded or reduced to reflect the set of features supported by the Policy Monitoring System.

[0148] Table I herein below lists possible severity codes, in the preferred embodiment.

TABLE I
Severity Code	Description
CRITICAL	Critical security violation, e.g., the network is
	undergoing an active security attack
HIGH	High-severity security violation, e.g., attempt to
	access sensitive data
MEDIUM	Medium-severity security violation, e.g., attempt
	to access a protected (but not highly sensitive)
	resource
WARNING	Low-severity security violation, e.g., an incorrect
	password was entered
MONITOR	A security violation was not detected but an
	unusual or potentially suspect network event has
	occurred, e.g., TELNET access to a public web
	server
INFORMATION	A perfectly valid network event is being reported
	for informational purposes only

[0149] It is noted that the list of severity codes included in Table I is by no means complete. In other embodiments, the set of severity codes is expanded or reduced to reflect the set of features supported by the Policy Monitoring System.

[0150] Table J herein below lists possible agent directives in the preferred embodiment.

TABLE J
Agent Directive	Description
DECRYPT	The Agent is instructed to decrypt all traffic at the
	current protocol layer
DISRUPT	The Agent is instructed to terminate and/or
	disrupt all subsequent traffic associated with this
	network event
LOG_TRAFFIC	The Agent is instructed to log all traffic at the
	current protocol layer

[0151] It is noted that the list of agent directives included in Table J is by no means complete. In other embodiments, the set of agent directives is expanded or reduced to reflect the set of features supported by the Policy Monitoring System.

[0152] Following are examples of preferred embodiments of dispositions:

	// Network event ok but should be logged
	( disposition Ok_Monitor	// disposition <name>
	( code OK)	// disposition code
	( log-directive	// logging directive
	MONITOR	// severity code
	“Monitored activity” )	// logging string
	)

[0153] The Ok_Monitor disposition is used to dispose of a valid network event 103 while flagging a logging subsystem that this event should be logged at a low severity level (MONITOR).

	// Decrypt SSL session data and continue processing network event
	( disposition Continue_Decrypt
	( code CONTINUE )
	( agent-directive DECRYPT )
	)

[0154] The Continue_Decrypt disposition is used to inform the Policy Engine 101 that additional information is needed from the Agent 102 before determining a final disposition 105 for the network event 103 while, at the same time, instructing an appropriate Agent to decrypt all traffic at a current protocol layer.

	// access to target resource is denied
	( disposition Access_Denied
	( code ACCESS_DENIED )
	( log-directive
	HIGH
	“Access denied” )
	)

[0155] The Access_Denied disposition is used as a final disposition 105 for a network event 103. It denotes a policy violation.

[0156] A list of built-in dispositions of the preferred embodiment is provided herein above in Table A.

[0157] Rules

[0158] In the preferred embodiment a rule object defines a policy rule. A policy rule governs a specific interaction, or set of interactions, between two communicating entities. The Policy Engine 101 evaluates policy rules against protocol events to determine if the latter conform to the active security policy.

[0159] Following is an example of a policy rule according to a preferred embodiment of the invention:

	( rule Tcp_Ext2Int	// rule <name>
	( description   “Communications from external hosts” )
	( agent Foo_Subnet_Monitor )	// the reporting agent
	( protocol TCP )	// the protocol
	( action CONNECT )	// the protocol action
	( initiator External_Hosts )	// the active principal
	( target Internal_Hosts )	// the passive principal
	( outcome
	( immediate	// the immediate outcome
	// if/ifnot <condition> <disposition>
	( if Catch_Suspect Security_Attack_Possible )
	( if Catch_Attacker Security_Attack_Progress )
	( default continue )	// using built-in disposition
	)
	( final	// the final outcome
	( default Ok_Monitor )
	)
	)
	)

[0160] In the preferred embodiment a policy rule comprises:

• • [0161] Agent—represents Agent 102 that reported the protocol event 103. The Agent 102 is denoted by a credential name. The policy rule is only considered if this credential is satisfied by the credentials presented by the reporting Agent 102. In the example above, Foo_Subnet_Monitor is the name of a credential object identifying one or more Agents. This field is optional. If omitted, the rule applies to all Agents.
  • [0162] Protocol—a protocol to which the rule is applicable. A protocol event 103 addresses one and only one protocol. This field is mandatory. Note that the special token ignore is used to denote a rule that applies to all protocols.
  • [0163] Action—a protocol action to which this rule is applicable. Each protocol comprises one or more several distinct actions (e.g. connect, transfer-data, release), some of which might be of interest to the security policy. A protocol event denotes one and only one protocol action. This field is mandatory. Note that the special token ignore is used to denote a rule that applies to all actions within the specified protocol.
  • [0164] Initiator—represents the active principal 141 in the protocol event 103. The initiator 141 is denoted by a credential name or by the special tokens absent (credentials must not be presented in the protocol event), present (credentials must be presented but their actual value is unimportant) and ignore (credentials may or may not be presented). In the example herein above, External_Hosts is the name of a credential object identifying one or more TCP/IP hosts. This field is mandatory.
  • [0165] Target—represents the passive principal 142 in the protocol event 103. The target 142 is denoted by a credential name or by the special tokens absent, present and ignore. In the example above, Internal_Hosts is the name of a credential object identifying one or more TCP/IP hosts. This field is mandatory.
  • [0166] Prerequisite—(not shown in the example above) one or more rules that must be satisfied by a previous protocol event. Prerequisite rules are identified by names. Prerequisites are used to place additional constraints on an entire network event 103. See an example herein that illustrates the use of prerequisites in rules. It should be noted that if two or more rules are listed as prerequisites, the prerequisite is satisfied if any of the listed rules taken in the order in which they are listed satisfies a previous protocol event. This field is optional.
  • [0167] Outcome—the outcome section defines what to do with the protocol (or network) 103 event if the current policy rule is applied to the protocol event. That is, if the rule is selected by the Policy Engine 101 as the most suitable for the protocol (or network) event. Every policy rule must have a disposition that applies to the protocol event and another disposition that applies to the entire network event. In some cases these are one and the same. The Policy Engine 101 evaluates the outcome and produces a disposition for either the protocol or the network event. There are two outcomes defined:
  • [0168] Immediate—an immediate outcome applies to the protocol event immediately. A policy rule may or may not include an immediate outcome.

[0169] If it does, the outcome is evaluated as soon as the rule is selected for the protocol event. If it does not, there is an implied disposition for the protocol event, a built-in disposition continue (see Table A for the definition) which instructs the Policy Engine 101 to continue processing the network event. If the immediate outcome generates a disposition with a disposition code other than CONTINUE, this disposition becomes the disposition for the entire network event. In this instance, the final outcome, defined herein below, will not be evaluated.

• • [0170] Final—an outcome that applies to the entire network event if this rule becomes a final rule evaluated for that event. The final outcome must be specified if the immediate outcome does not generate a final disposition for the network event. If it is not, an implied disposition for the network event, the built-in disposition policy-error, see Table A for the definition, denotes a policy specification error. The final outcome is evaluated when the Policy Engine determines that no additional protocol events are to be considered for the current network event. The final outcome must always generate a final disposition, i.e. a disposition with a disposition code of CONTINUE is not allowed in a final outcome.

[0171] In the preferred embodiment each outcome section comprises one or more conditional statements, each followed by a disposition. The purpose of conditional statements is to specify constraints upon a protocol event, or special conditions that, if satisfied, cause the generation of an alternate disposition for the protocol (or network) event. Conditional statements are evaluated in the order in which they are specified within the outcome section.

[0172] In the preferred embodiment a conditional statement starts with one of the following keywords:

• • [0173] if—takes as arguments a condition and a disposition, each referenced by name. If the condition evaluates to TRUE, the disposition becomes the disposition for the protocol event.
  • [0174] ifnot—takes as arguments a condition and a disposition, each referenced by name. If the condition evaluates to FALSE, the disposition becomes the disposition for the protocol event.
  • [0175] default—takes a single argument, a disposition referenced by name. It is equivalent to a condition that is always satisfied, thereby triggering the disposition that is its argument. This conditional statement is mandatory and must be the last conditional statement in an outcome.

[0176] The following examples illustrate the use of prerequisites in rules in a preferred embodiment. The first rule is the prerequisite.

	( credential Host_A
	( assertion
	( and
	( eq ip-address 207.5.63.8 )
	( eq ip-port 80 )
	)
	)
	)
	( rule Access_Host_A
	( protocol TCP )
	( action CONNECT )
	( initiator ignore )
	( target Host_A )
	( outcome
	( final
	( default Access_Denied )  // Access_Denied
	defined above
	)
	)
	)

[0177] Herein above, the rule Access_Host_A states that access to host A on port 80 by any host is denied, unless explicitly allowed by a rule at a higher protocol layer. Note the use of a final outcome, which is only evaluated if Access_Host_A becomes the applicable rule for the entire network event. The implied disposition for the protocol event is CONTINUE.

[0178] This rule can be overridden by another rule at the HTTP layer stating that access is allowed to host A on port 80, as shown below:

( rule Http_To_Host_A
( protocol HTTP )
( action ignore )
( initiator ignore )
( target ignore )
( prerequisite Access_Host_A ) // reference to rule above
( outcome
( immediate
( default ok )       // using built-in disposition
)
)
)

[0179] The end result of the two policy rules herein above is to prevent all access to host A on port 80 unless that access is using HTTP over TCP/IP.

[0180] In the preferred embodiment a prerequisite rule is any rule that is selected for a previous protocol event. This includes rules in the same protocol layer. As an example, to ensure that a web server requires HTTP authentication before allowing access to a specific web page, use the following rules:

	( credential Some_Url
	( assertion
	( prefix url “//myserver.com/Documents” )
	)
	)
	( rule Host_A_Anon_Access
	( protocol HTTP )
	( action ( union GET POST ) )
	( initiator absent )
	( target Some_Url )
	( prerequisite Access_Host_A ) // from example above
	( outcome
	( final
	( default Access_Denied )  // Access_Denied
	defined above
	)
	)
	)
	( condition Require_Auth
	( description   “Check if server returned the Unauthorized
	response” “code” )
	( assertion
	( eq http-status-code 401 )
	)
	)
	( rule Check_Access_Denial
	( protocol HTTP )
	( action RESPONSE )
	( initiator ignore )
	( target ignore )
	( prerequisite Host_A_Anon_Access )
	( outcome
	( immediate
	( ifnot Require_Auth Access_Denied )
	( default ok )  // using built-in disposition
	)
	)
	)

[0181] The example herein above shows that access to the document sub-tree identified by Some_Url requires the user be authenticated using basic HTTP authentication. The authentication is accomplished by means of the condition Require_Auth which, in the context of rule Check_Access_Denial, checks that the server returns an Unauthorized status code. If the server fails to do so, the Access_Denied disposition is generated. Note that the prerequisite constraint ensures that the rule Check_Access_Denial is only considered if the rule Host_A_Anon_Access is selected when the HTTP request event is evaluated, that is, requests where basic HTTP authentication is not used.

[0182] The Policy Specification Process

[0183] In the preferred embodiment the policy specification process comprises the following steps:

[0184] 1) Identify communicating entities recognized by the security policy. The entities comprise physical networks and sub-networks, host machines, communication protocols, users, applications, services, and any other resources of interest.

[0185] 2) Identify relationships between the communicating entities and define rules to control said relationships (e.g. host A may communicate with host B. but not with host C).

[0186] 3) Formally define communicating entities and entity relationships using the policy specification language (FIG. 1; 108) according to the invention. In a preferred embodiment a visual tool is used. In another embodiment a text-based editor is used. In the preferred embodiment the output of this step is a policy specification in an advanced encoding format according to the invention.

[0187] 4) Compile the policy specification with a Policy Compiler (FIG. 1, 106). In one embodiment, said compilation step is incorporated into a graphical policy editor, such that it is incorporated into said policy specification step. In another embodiment it is a distinct step. This step comprises:

• • [0188] a) Checking the specification for errors of syntax or semantics;
  • [0189] b) Checking the specification of credentials for errors (e.g. credentials that can never be satisfied);
  • [0190] c) Checking the specification of conditions for errors (e.g. conditions that can never be satisfied);
  • [0191] d) Checking the specification of rules for completeness and coverage;
  • [0192] e) Ordering credentials based on their specificity (described in detail herein below);
  • [0193] f) Ordering rules based on the credentials of their principals (described in detail herein below); and
  • [0194] g) Resulting in an annotated policy specification (FIG. 1, 109) represented by a text file (FIG. 1 107).

[0195] The annotated policy specification 107 is suitable for loading into the Policy Engine 101 for evaluation of one or many network events 103, or back into the graphical policy editor for visualization and further refinement.

[0196] Evaluation of Rules

[0197] This section describes how policy rules are organized and evaluated according to the invention.

[0198] Policy Evaluation Model

[0199] The policy specification language 108 alone does not describe how the Policy Engine 101 evaluates policy rules. In the preferred embodiment of the invention, a security administrator that writes the policy specification 107 and the Policy Engine 101 that enforces the policy specification 107 share a common view of the evaluation procedure. The evaluation of policy rules is deterministic.

[0200] In the preferred embodiment of the invention the basic policy specification language 108 is augmented to convey information about how rules are ordered for purposes of evaluation, i.e. which rules are evaluated first and which rules are selected for any given network event. The augmented language is a superset of the basic specification language 108 and it is hereinafter referred to as the annotated specification language 109.

[0201] In one embodiment the security administrator uses the annotated specification language 109 using a visual tool, such as a graphical policy editor to determine how the policy rules are interrelated, their hierarchical relationships and how they will be evaluated. This step is crucial to determining whether the specified policy correctly reflects the desired security policy and to identifying areas where the policy specification needs refinement.

[0202] In the preferred embodiment the Policy Engine 101 uses the annotated language 109 to organize the policy, after having converted it to an internal representation in a manner best suited for the efficient evaluation of network events.

[0203] In the preferred embodiment the Policy Engine 101 receives protocol events in proper sequence: Protocol events for protocols lower in the protocol stack are received before protocol events for protocols higher in the stack. This sequencing is important because the Policy Engine 101 must make a policy decision about, for example, a TCP connection, before it makes a decision about an SSL session that uses that TCP connection.

[0204] Data about a specific protocol event may not arrive all at once. For example, when evaluating an SSL session the Policy Engine 101 first receives the server certificate and negotiated ciphersuite before receiving a client certificate or a message indicating that none was provided. In a preferred embodiment, the Policy Engine 101 uses incomplete information about a protocol event in order to collect a set of possible policy rules applicable to that event. However, for the sake of simplicity, the remainder of this document assumes that Agents convey information about protocol events in an atomic manner.

[0205] In the preferred embodiment for every protocol event the Policy Engine 101 selects a policy rule applicable to that event. Every policy rule is associated with a specific protocol and action or a set of protocols and actions. Therefore only the set of rules relevant to the protocol event is considered. Of that set, several rules can be satisfied by the event. In the preferred embodiment a policy rule is satisfied by a protocol event if the following holds true:

[0206] 1) The credentials of the Agent 102 reporting the event match the rule's agent credentials (if any), defined as a set of attribute-value assertions.

[0207] 2) The rule's protocol specifier matches the protocol identifier in the protocol event.

[0208] 3) The rule's action specifier matches the action identifier in the protocol event.

[0209] 4) The rule's prerequisite clause is satisfied (details described herein below).

[0210] 5) The credentials of the initiator 141 and target 142 principals in the protocol event satisfy the rule's corresponding credentials, defined as a set of attribute-value assertions.

[0211] In the preferred embodiment when several rules are satisfied by a protocol event, the Policy Engine 101 selects a rule that is most specific to the protocol event.

[0212] The specificity of a policy rule is determined by the specificity of the credentials associated with the policy rule, as well as the specificity of the rule's protocol, action and prerequisite specifiers. For example, a rule that targets one single protocol is more specific than a rule that targets all protocols. In another example, a rule that specifies a prerequisite is more specific than a rule that does not.

[0213] In the preferred embodiment the specificity of a credential specification is determined by the set relationships of said specification with other credential specifications. Following are examples of credential specifications:

• • [0214] A: all principals with blue eyes
  • [0215] B: all principals with blue eyes and black hair
  • [0216] C: all principals with black hair

[0217] B defines the intersection of A and C, i.e. B is a subset of both A and C. Thus, B is more specific than either A or C.

[0218] According to the invention, in general, the more data described about a principal the more specific are the credentials. In the preferred embodiment, some attributes of a principal's credentials have more importance than do other attributes of the credentials. In the preferred embodiment the importance of an attribute is represented by its weight. The attribute weight is determined by its role as a discriminator of principals. For example, an attribute that yields a small set of principals has more weight than an attribute that yields a larger set of principals. In the hair and eye color example herein above, it is arbitrary to give a higher weight to eye color versus hair color or to give both hair and eye color the same weight. Assigning an attribute weight is easier because typically protocol credentials are structured hierarchically. For example, in the TCP protocol, the IP address attribute has clearly more weight than the IP port attribute because the number of principals with a given IP address is generally much smaller than the set of principals with a given port number.

[0219] In the preferred embodiment attributes that comprise a set of credentials are ranked by weight and the combined weight of all attributes in a credential specification is considered in determining a relative specificity of said specification.

[0220] In the preferred embodiment a policy specification has sets of credentials each of which are ranked at a same specificity level, thereby rendering many policy rules that are applicable to a given protocol event. Herein below is provided a section describing a number of practical guidelines for good policy development that minimize herein above ambiguities.

[0221] FIG. 5a is a schematic diagram of the preferred embodiment in which a network event 103 comprises M protocol events at different protocol layers, and in which the network event 103 has an associated network event disposition 105.

[0222] FIG. 5b is an algorithm showing how the M protocol events at different protocol layers of the network event 103 result in pending rules with or without immediate outcomes and, finally, a final disposition for the network event 105. For clarity, the algorithm assumes that the Policy Engine 101 always finds a policy rule applicable to a given protocol event, that at least a first Protocol Event (1) exists, and that the algorithm ends when the Agent 102 informs the Policy Engine 101 that no further protocol events will be generated. These assumptions are for clarifying purposes only and do not limit the invention in any way.

[0223] The algorithm begins with j=1 (500) and with the Policy Engine 101 receiving Protocol Event (1) from the Agent 102 (501) (502).

[0224] Once a most specific policy rule is selected for a given protocol event (503), the

[0225] Policy Engine 101 consults an outcome clause (504) determining if an immediate outcome is applied to the protocol event. In the preferred embodiment an immediate outcome applies to a protocol event while a final outcome applies to a network event (103).

[0226] In the preferred embodiment an immediate outcome is executed when it is specified. The immediate outcome can evaluate constraints (i.e. conditions) against a protocol event, produce a set of agent directives (e.g. instructing the Agent 102 to decrypt all subsequent traffic), and produce a final disposition (506) for the protocol event rendering said disposition for the entire network event. When a disposition of an immediate outcome is not a final disposition, a special disposition code, CONTINUE, is used as an indicator. All disposition codes other than CONTINUE denote final dispositions.

[0227] In the preferred embodiment when an immediate outcome does not produce a final disposition the associated selected policy rule becomes a pending policy rule for the related network event (507). The Policy Engine. 101 then waits for further protocol events of the network event 103 from the Agent 102 (508) and (501). In this embodiment, said pending policy rule is overridden by subsequent policy rule selected for a protocol event higher in the associated protocol stack (507).

[0228] In the preferred embodiment policy evaluation ends in one of two cases. First case is when no further rules in the policy apply to a network event (e.g. a highest protocol in the stack is reached). Second case is when the Agent 102 informs the Policy Engine 101 that no further protocol events will be generated (502) (509) (506) (510). In either case, a policy decision is then expected for the entire network event. The Policy Engine 101 selects a pending policy rule for a protocol highest in the protocol stack and executes the final outcome defined for that rule (511). In the preferred embodiment constraints are evaluated against the entire network event. In the preferred embodiment a final outcome always produces a final disposition (509) which becomes a disposition for the network event (506).

[0229] In the preferred embodiment a protocol event must result in a selection of a policy rule (pending or final). When a policy rule applicable to a given protocol event is not found, the Policy Engine 101 produces a special disposition identifying a policy specification error. See the default policy rule in Table A.

[0230] Ordering of Credentials

[0231] In the preferred embodiment credentials are ordered based on a combined weight of all attribute-value assertions that make up a credential specification.

[0232] In the preferred embodiment computing a weight of an attribute-value assertion of an attribute requires the following two steps:

[0233] 1) Assigning a ranking value to the attribute. Attributes that are listed in a credential specification are ranked against each other. Ranking is based on a value of the attribute as a discriminator of principals identified by the credentials. If the presence of the attribute in a credential specification generally yields a smaller set of principals than the presence of another attribute, then the former has a higher ranking than the latter.

[0234] 2) Assigning a ranking value to an assertion type of the attribute. An assertion type is used to make an assertion about the value of an attribute (e.g. eq, substring, range). Following are five assertion types, in decreasing ranking order:

• • [0235] a) Absent—an assertion not satisfied by any attribute value. The attribute is absent from the presented credentials. In one embodiment said assertion type typically is used to require the absence of an entire set of credentials (e.g. “no SSL client certificate”).
  • [0236] d) Single-value—an assertion satisfied by a single attribute value (e.g. “hair color is blue”).
  • [0237] e) Multi-value—an assertion satisfied by any value within a set of attribute values (e.g. “port number in the range of 3200 to 4200”).
  • [0238] d) Present—an assertion satisfied by any attribute value, wherein the associated attribute must be present in associated presented credentials.
  • [0239] e) Ignore—an assertion always satisfied, irrespective of whether the associated attribute is present or absent from associated presented credentials. This is a “don't care” matching rule.

[0240] Table K herein below shows the preferred embodiment assertion types for all operations that operate on attributes to build assertions. In the preferred embodiment when a credential specification does not include any assertions about a particular attribute then the assertion type for that attribute is ignore.

	TABLE K
	Operation	Assertion Type
	absent	Absent
	eq	Single-value
	ge	Multi-value
	gt	Multi-value
	has	Multi-value
	ip-mask	Multi-value
	ip-range	Multi-value
	le	Multi-value
	lt	Multi-value
	member	If the union has a single terminal member,
		the assertion type is single-value,
		otherwise it is multi-value
	prefix	Multi-value
	present	Present
	range	Multi-value
	root	Multi-value
	substring	Multi-value

[0241] In the preferred embodiment assertions in a credential specification often are combined using logical operators and, or and not. For example,

	( credential Credentials_Example_1
	( assertion
	( and
	( eq ip-address 207.5.63.8 )
	( or
	( eq ip-port 80 )
	( gt ip-port 443 )
	)
	)
	)
	)

[0242] In the preferred embodiment a weight assigned to a credential specification is derived from a combined weight of all assertions the credential specification comprises. An algorithm herein below is used recursively to compute a combined weight of a set of assertions operated on by a logical operator:

[0243] A. An operator not does not affect the weight of its operand.

[0244] B. An operator and creates a union of weights of all its operands. The weights are sorted in decreasing order of attribute rank. If multiple assertions are made about a particular attribute, use a weight of a most specific assertion and discard all other weights for that attribute. If multiple distinct assertions (i.e. not identical or equivalent) are made about a particular attribute at a same level of specificity, the assertions are enumerated. In general, the higher a number of distinct assertions made about an attribute the more specific is a credential specification. For example, the two assertions “hair is not black” and “hair is not brown” when combined in a union are more specific than either individual assertion.

[0245] C. An operator or results in a selection of an operand with a lowest weight. In addition said combined weight is penalized, such that it weighs less than the associated assertion with the lowest weight. If two or more assertions of equal weight are combined with or, the combined weight is lower than that of either or any individual assertion. The rationale behind the penalty is that, in general, combined assertions yield a larger set of principals (i.e. is less specific) than each assertion by itself. The weight penalty is associated with the entire credential specification, not with an individual assertion or set of assertions. Thus, for every instance of the operator or in the credential specification, the weight penalty is incremented by one.

[0246] In the preferred embodiment a 3-tuple represents a weight of all attribute-value assertions about a specific attribute within a credential specification. Elements in the 3-tuple are:

• • [0247] Attribute rank
  • [0248] Assertion type rank
  • [0249] Attribute assertion count

[0250] In the preferred embodiment the 3-tuple is represented by a weight S-expression in the annotated specification language. A syntax of this expression is:

• • [0251] (weight<attribute><assertion-type><assertion-count>)

[0252] In the preferred embodiment ranking of assertion types is fixed and defined by the Table L following:

	TABLE L
	Assertion Type	Rank
	absent	4
	single-value	3
	multi-value	2
	present	1
	ignore	0

[0253] In the preferred embodiment ranking of an attribute is configurable by a security administrator and must be defined prior to a compilation of a policy specification. Attribute ranking is communicated to the policy compiler in a variety of ways. Table M herein below shows a preferred embodiment of proposed rankings for attributes used in credentials for all supported protocols. Said rankings are assumed in examples used throughout the remainder of this document. It is noted that a credential attribute agent-attributes cannot be used in a specification of an initiator or target credential and therefore need not be ranked. It is further noted that the special assertions true and false, which are allowed by the policy specification language's grammar in the preferred embodiment, do not apply to any specific attribute and, thus, are assigned a special weight consisting of a zero valued attribute rank, a zero valued assertion type rank and a zero valued attribute assertion count.

	TABLE M
	Protocol/Action	Attribute	Rank
	IP/ASSOCIATION	mac-address	3
	UDP/ASSOCIATION
	ICMP/ASSOCIATION	ip-address	2
	TCP/CONNECT	ip-port	1
	SSL/HANDSHAKE	der-cert	5
		x509-subject	4
		x509-issuer	3
		x509-cert-path	2
	SSL/HANSHAKE	cert-status	1
	HTTP/GET	http-username	3
	HTTP/POST	http-password	2
	HTTP/HEAD	url	1

[0254] In the preferred embodiment an attribute assertion count starts at zero for a first assertion and is incremented monotonically for all subsequent assertions. That is, the count enumerates additional assertions for the attribute. In the preferred embodiment the assertion count is omitted from the weight S-expression when said count is zero.

[0255] In the preferred embodiment a weight S-expression is omitted when an assertion type is ignore.

[0256] In the preferred embodiment the three elements of a 3-tuple are used in sorting a collection of 3-tuples. The attribute rank as a primary key, the assertion type rank as a secondary key, and the attribute assertion count as a tertiary key produce an ordered list of 3-tuples sorted in decreasing order of rank and count. In the preferred embodiment said sorted list is used to rank credential specifications against each other. The sorting algorithm is described using pseudo-code in Table N herein below:

	TABLE N
	Sort_3tuples: subroutine ( 3tuple A, 3tuple B )
	begin
	if A.attribute_rank > B.attribute_rank
	return (A is greater than B);
	else if A.attribute_rank < B.attribute_rank
	return (A is less than B);
	else   // same attribute rank
	if A.assertion_type > B.assertion_type
	return (A is greater than B);
	else if A.assertion_type < B.assertion_type
	return (A is less than B);
	else   // same assertion type
	if A.assertion_count > B.assertion_count
	return (A is greater than B);
	else if A.assertion_count < B.assertion_count
	return (A is less than B);
	else   // same assertion count
	return (A is equal to B);
	end

[0257] A weight penalty is represented by the following S-expression in the annotated specification language:

• • [0258] (weight-penalty <penalty-count>)
    where <penalty-count> is an integer representing a number of or operators in a credential specification.

[0259] Thus, Credentials_Example_—1 herein above is annotated as follows:

	( weight ip-address single-value )
	( weight ip-port multi-value )
	( weight-penalty 1 )

[0260] In the preferred embodiment a credential specification can combine previous credential specifications with each other or with additional assertions. In the preferred embodiment rules for a combination of assertions with logical operators apply equally to a combination of credential specifications. For example:

	( credential Credentials_Example_2
	( assertion
	( eq ip-address 207.5.63.22 )
	)
	)
	( credential Credentials_Example_3
	( assertion
	( and
	Credentials_Example_2
	( gt ip-port 42 )
	)
	)
	)
	( credential Credentials_Example_4
	( assertion
	( and
	( or
	Credentials_Example_1
	Credentials_Example_3
	)
	( It ip-port 1025 )
	)
	)
	)

[0261] The weight of Credentials_Example_—2 is:

• • [0262] (weight ip-address single-value)

[0263] The weight of Credentials_Example_—3 is:

• • [0264] (weight ip-address single-value)
  • [0265] (weight ip-port multi-value)

[0266] In the embodiment to compute the weight of Credentials_Example_—4 first compute a weight of the or expression. Credentials_Example_—1 is selected as having a lowest weight because of an associated weight penalty. Furthermore, the or expression in Credentials_Example_—4 increases the weight penalty further, yielding:

	( weight ip-address single-value )
	( weight ip-port multi-value )
	( weight-penalty 2 )

[0267] In the embodiment the and expression adds an additional, distinct, assertion about ip-port. The assertion is of the same type as one currently selected because they are both multi-value assertions. The assertion count for ip-port is incremented, yielding:

	( weight ip-address single-value )
	( weight ip-port multi-value 1 )
	( weight-penalty 2 )

[0268] In the embodiment a ranking algorithm for comparing and ordering credentials is implied in the example previously described herein above. Following in Table O is an associated algorithm using pseudo-code:

TABLE O
Rank_credentials: subroutine ( credentials A, credentials B )
begin
Let X be a sorted list of 3-tuples that describe the weight of credential
specification A;
Let Y be a sorted list of 3-tuples that describe the weight of credential
specification B;
// compare 3-tuples
for all i in X do
R = Sort_3tuples(X[i],Y[i]);  // defined above
if R is greater-than
return (A ranks higher than B);
else if R is less-than
return (A ranks lower than B);
else
continue;  // 3-tuples are equal
end
// X and Y are the same; compare weight penalties
if A.weight_penalty < B.weight_penalty
return (A ranks higher than B);
else if A.weight_penalty > B.weight_penalty
return (A ranks lower than B);
else
return (A and B have the same rank);
end

[0269] The following Table P ranks example credentials according to the preferred embodiment using the algorithm herein above. A weight column shows 3-tuples using a format W:x,y,z, wherein x is an integer value for an attribute rank (Table

[0270] M), y is an integer value for an assertion type (Table P), and z is an assertion count. A weight penalty is shown as P:x, wherein x is a penalty count. It is noted that the higher a rank of a credential specification, the more specific it is. For completeness, the table includes ranking for built-in credentials denoted by absent, present and ignore. Said built-in credentials make assertions about and in the order of an absence, presence, and irrelevance of any credentials presented by a protocol event. It is noted that in the preferred embodiment ignore and present always rank lower and absent higher than do any user-defined credentials.

	TABLE P
	Name	Weight	Rank
	absent (built-in)	W: *, 5	6
	Credentials_Example_4	W: 2, 3	5
		W: 1, 2, 1
		P: 2
	Credentials_Example_3	W: 2, 3	4
		W: 1, 2
	Credentials_Example_1	W: 2, 3	3
		W: 1, 2
		P: 1
	Credentials_Example_2	W: 2, 3	2
	present (built-in)	W: *, 1	1
	ignore (built-in)	W: *, 0	0

[0271] Ordering of Rules

[0272] In the preferred embodiment policy rules must be organized such that when two or more rules are satisfied by a protocol event, the most specific rule for that event is selected. The specificity of a policy rule is fully determined by the specificity of the credentials it uses.

[0273] In the preferred embodiment policy rules are organized as follows:

• • [0274] 1) Rules are segregated by protocol. For example, rules that apply to a TCP protocol are separated from those that apply to a SSL protocol.
  • [0275] 2) Within each protocol group, rules are segregated by action. For example, rules that only apply to a TCP CONNECT action are separated from those that only apply to a TCP CLOSE action.
  • [0276] 3) Within each protocol-action group, rules are ranked by the specificity of their respective credentials. The ranking algorithm is:
    • [0277] a) Create a 2-tuple from a ranking order of an initiator credential and a target credential. The first element in said 2-tuple is a highest-ranking value and the second element a lowest. That is, said 2-tuple is defined as (MAX(I,T), MIN(I,T)), wherein I and T are the ranking values for the initiator and target credentials, respectively.
    • [0278] b) Sort the rules in increasing ranking order using the first element in the 2-tuple as the primary sorting key and the second element as the secondary key. Rules with identical 2-tuples are given the same ranking number. The rule or rules with the highest-ranking number is the most specific rule for the protocol group.

[0279] In the preferred embodiment and because rules are ranked directly from the ranking of their credentials, a special representation is not provided in the annotated specification language for the ranking of the policy rules.

[0280] Following is an example using credentials from herein above:

	( rule Rule_Example_1
	( protocol TCP )
	( action CONNECT )
	( initiator Credentials_Example_2 ) // ranked #2
	( target Credentials_Example_1 )   // ranked #3
	( outcome
	...
	)
	)
	( rule Rule_Example_2
	( protocol TCP )
	( action CONNECT )
	( initiator Credentials_Example_1 ) // ranked #3
	( target Credentials_Example_2 )   // ranked #2
	( outcome
	...
	)
	)
	( rule Rule_Example_3
	( protocol TCP )
	( action CONNECT )
	( initiator Credentials_Example_2 ) // ranked #2
	( target Credentials_Example_4 )   // ranked #5
	( outcome
	...
	)
	)

[0281] Table Q herein below shows how said rules are ranked according to the invention.

	TABLE Q
		Credentials
	Name	Rank	Rule Rank
	Rule_Example_3	(T: 5, I: 2)	2
	Rule_Example_1	(T: 3, I: 2)	1
	Rule_Example_2	(I: 3, T: 2)	1

[0282] It is noted that Rule_Example_—1 and Rule_Example_—2 are ranked at the same specificity level. This does not represent a problem because the respective initiator and target credential sets are non-intersecting and used in different roles.

[0283] In the preferred embodiment it is possible for two or more rules at a same specificity level to be satisfied by a single protocol event. During policy specification a security administrator disambiguates the evaluation of rules with the same specificity level by forcing a ranking order among them. Forcing a ranking order is done by specifying that one rule is ranked above another rule and is termed forced ranking. Forced ranking is expressed by means of the following S-expression:

• • [0284] (rank-above <rule-name>)

[0285] For example, to give Rule_Example_—2 precedence over Rule_Example_—1, the following S-expression is added to a definition of Rule_Example_—2:

• • [0286] (rank-above Rule_Example_—1)

[0287] In the preferred embodiment after performing the standard ranking algorithm herein above, the Policy Engine 101 evaluates all rank-above expressions and reassigns ranking numbers to each rule accordingly. In the preferred embodiment it is important to note that forced ranking does not force a ranking of an affected rule to a level of a more specific rule higher in the ranking order. Instead a new ranking level is created for the affected rule and all other ranking numbers of more specific rules are incremented accordingly.

[0288] For example, Rule_Example_—2 herein above is given ranking number 2 and the ranking number of Rule_Example_—3 herein above is incremented from 2 to 3.

[0289] In the preferred embodiment forced ranking is applied to any rule and is not limited by rules having only non-unique ranking numbers. In this embodiment security administrators are cautioned not to use said forced ranking feature unless absolutely necessary. Its misuse may result in a policy specification that is both difficult to manage and difficult to evaluate. In the preferred embodiment runtime conflicts in the evaluation of rules (i.e. when a protocol event is satisfied by multiple rules) typically can be solved by redesigning credentials upon which said rules are based. Useful tips are provided herein below.

[0290] Evaluation Algorithm

[0291] In the preferred embodiment the Policy Engine 101 applies a policy evaluation algorithm to each incoming protocol event. The algorithm results in a selection of a policy rule applicable to the protocol event and may produce an immediate or final disposition.

[0292] Following is a step-by-step description of the evaluation algorithm according to the preferred embodiment. It is noted that the evaluation procedure described herein below is in conceptual form and does not take into account any possible runtime optimizations:

• • [0293] 1) Select a set of rules applicable to an Agent reporting an event;
  • [0294] 2) From said set, select a second set of rules applicable to an associated examined protocol.
  • [0295] 3) From said second set, select a third set of rules applicable to an associated examined protocol action.
  • [0296] 4) Starting with a most specific policy rule in said third set and descending to a least specific rule find a policy rule satisfied by said protocol event. A matching algorithm according to the preferred embodiment is as follows:
    • [0297] a) If one or more orderly listed prerequisite rules are specified, ensure at least one of said prerequisite rules is satisfied by a previously processed protocol event. In the preferred embodiment a prerequisite rule is satisfied if it is a pending policy rule for the protocol event.
    • [0298] b) Match initiator and target credentials in the policy rule against the corresponding initiator and target credentials presented in the protocol event.
  • [0299] 5) If a policy rule satisfying the protocol event is not found the Policy Engine 101 generates a disposition for the network event indicating that a policy specification error was encountered. Effectively the processing of the network event thereby terminates.
  • [0300] 6) If a policy rule satisfying the protocol event is found, the Policy Engine 101 checks for other rules having a same ranking number and also satisfying the event. If such rules are found the Policy Engine 101 uses the following algorithm in the preferred embodiment to select a single applicable rule:
    • [0301] a) Rules that specify all protocols (Le. using ignore or present) are less specific than rules that explicitly list a set of one or more protocols.
    • [0302] b) Rules that specify all actions (i.e. using ignore or present) are less specific than rules that explicitly list a set of one or more actions.
    • [0303] c) Rules that have prerequisites are more specific than rules that do not have prerequisites. Rules that specify a higher-ranking prerequisite are more specific than rules that specify a lower-ranking prerequisite. In the preferred embodiment a ranking relationship is relevant only if both prerequisite rules belong to a same protocol-action group.
    • [0304] d) If thereafter a single rule is determined as more specific than the others it is selected for the protocol event. If more than one rule remains the Policy Engine 101 sorts the remaining rules in increasing lexical order by name and selects a first rule from the sorted rules having an immediate disposition indicating in decreasing order of precedence:
      • [0305] i) a policy violation (any disposition code other than OK or CONTINUE);
      • [0306] ii) CONTINUE (allows other rules to examine further the network event); and
      • [0307] iii) OK

[0308] The outcome of the policy evaluation algorithm herein above is a policy rule that satisfies the protocol event. If an immediate outcome is specified for that rule, it is executed, producing a disposition for the protocol event. If the disposition comprises a final disposition code (any code other than CONTINUE), the disposition is also the final disposition for the network event.

[0309] Otherwise in the preferred embodiment the selected policy rule is a pending policy rule for the network event. In absence of any further protocol events the pending policy rule is promoted to selected policy rule. A final outcome of the selected policy rule is executed producing a final disposition for the network event.

[0310] Policy Specification Guidelines

[0311] Provided herein below in Table R are a number of practical guidelines coupled to the preferred embodiment for the development and specification phases of a security policy. Adhering to the guidelines ensures efficient and accurate evaluation of a policy by the Policy Engine 101. It is intended to incorporate the guidelines into a graphical policy editing invention using wizards, policy templates and other UI mechanisms that among other uses simplify and direct the policy specification process.

TABLE R
Rule #1: Work on group relationships
The first step in policy specification is identifying the communicating entities and resources that
interact with each other over the network, that is to say, specifying the credentials for both initiator
and target principals. Defining groups in relation to each other can significantly enhance the
ranking of credentials. This is best done by:
Defining all large groups first (e.g. all hosts in the corporate network, all valid certificates).
Defining all other groups by subsetting larger groups (e.g. all hosts in the marketing
subnetwork, all certificates issued by the corporate CA, all revoked certificates).
The process of defining a group as a subset of another can be thought of as the process of
specializing the credentials specification for the larger group. Thus, the smaller group's credentials
are more specific than those of the larger group. Likewise, creating a larger group through the
union of smaller groups generalizes the credentials specification of the smaller groups, thus
resulting in less specific credentials for the larger group.
Rule #2: Deny first, allow later
A good security management principle is that of denying access to a resource unless access is
explicitly granted. Thus, when specifying a network's security policy the first step must be to deny
access to all target principals via rules that identify initiators via the broadest possible credentials.
One can then grant access to each target principal solely to the group of principals to which access
should be granted.
For example, to protect a set of host machines from access by all but a small set of principals, one
can define a rule that denies access to these machines and whose initiator is denoted by ignore. A
second rule allowing access can then be defined. It specifies the same target principal and, as the
initiator, a credential specification that describes, in the narrowest possible manner, the principals
being granted access. The ranking algorithm guarantees that the rule granting access ranks higher
than the rule denying it.
It is crucial that the credential specification for the principals being granted the access privilege be
as specific as possible, with all other principals being denied access. This ensures that access is
not inadvertently granted to non-privileged principals.
In general, the first policy rule in every protocol layer is one that denies access to all and by all
communicating entities (using ignore for both initiator and target principals) for all protocol actions
(again using ignore).
Rule #3: Prerequisites are your friends, use them often and use them wisely
Prerequisite rules can play a critical role in the disambiguation of like-ranked rules. Thus,
prerequisites should be used whenever possible. In particular, prerequisites should be used in a
way that targets each rule to the smallest set of principals possible, and that prevents the repetition
of credentials within a set of related rules. For example, if an IP rule exists that defines
communication between hosts in two subnets and we want to define a TCP rule affecting the same
set of hosts, we should define a TCP rule that takes the aforementioned IP rule as a prerequisite.
In addition, the credentials used in the TCP rule should not include assertions that repeat what has
already been established by the IP rule (e.g. the IP addresses of the relevant hosts). Instead the
TCP rule credentials should specialize (if so desired) the specification of the host credentials, e.g.
limiting the host services covered by the rule (i.e. stating the IP ports of interest).
Rule #4: Make dispositions final, unless they are not
Immediate outcomes that produce a final disposition should be used whenever possible. In other
words, unless one knows that a rule at a given protocol layer may be overridden by a specific rule
at a higher protocol layer, the immediate outcome for the former rule should always produce the
final disposition for the network event. This prevents a rule's outcome from being inadvertently
subsumed by another protocol event.
In general, unless a rule is explicitly listed as a prerequisite rule for another rule higher in the
protocol stack, its immediate outcome should produce the final disposition for the network event.
Rule #5: If you know the Agent, name it
If a policy rule only applies to communications within a specific network segment, restrict the rule's
scope by specifying the Agent(s) reporting the protocol events for which this rule should be
considered.
By doing so, one eliminates that rule from being considered in events reported by other Agents.

[0312] An Exemplary Policy Development System

[0313] The Policy Developer Studio

[0314] A policy development system comprises a suite of tools for developing policy. The policy developer studio is one such policy development system. The policy developer studio is based on a core object model, referred to simply as meta-policy. The policy developer studio provides a higher level of abstraction than that provided by the policy specification language (FIG. 1 108). That is, the policy developer studio allows network security policy to be developed using a logical and comprehensive view of network traffic rather than using a point view as provided by firewalls, routers and authorization systems. Computers and users are modeled in terms of their common functionality and by the services they provide and require from each other. The invention enables customers to specify formally the business practices and security policies governing the network operation. Network traffic is evaluated against the policy specification providing actionable information to mitigate security risk and improve network operation.

[0315] The policy developer studio simplifies creation and maintenance of security policies. In the preferred embodiment of the invention, the policy developer studio comprises a policy developer graphical user interface (GUI) tool that provides a front end to the policy language of patent application, A Declarative Language for Specifying a Security Policy, U.S. patent application Ser. No. 09/479,781 filed Jan. 7, 2000 described herein above. By using the policy developer GUI tool, a user need not be concerned with the mechanics of the policy language.

[0316] The preferred embodiment of the policy developer studio is described with reference to FIG. 6, a schematic diagram of a policy developer studio 600 according to the invention. At the center of the diagram and at the core of the studio is a meta-policy core object 601 comprising a plurality of network-related objects, details of which are described below in the section, The Meta-Policy Model.

[0317] The meta-policy core object 601 is flexible and adaptable to provide for a plurality of translations and/or output that can depend on various desired usage and need. One such optional translation is an XML file 602a that preserves, i.e. saves, the state of a current network policy represented by the meta-policy core object 601 at a given time. Moreover, the XML output provides a standardized and interoperable representation of the meta-policy data, thus allowing it to be loaded and, potentially, manipulated by other software applications. Another optional, yet equally preferred output of the meta-policy core object 601 is, after a compilation step, a compiled file, the contents of which represent the given network policy in the policy specification language (FIG. 1 107) suitable for input into a policy engine (FIG. 1 101). A third optional translation is a policy description document 602c that provides a human readable representation of the given network policy. It should be appreciated that other translations and outputs are possible and are within scope of the invention.

[0318] The preferred embodiment of the invention provides a graphical user interface (GUI) tool 603 that represents, among other items, the network-related objects within the meta-policy core object 601 that themselves are used to represent the network security policy. By using the GUI tool 603, referred to herein as the policy developer GUI tool or application, a user can develop network security policy using a novel logical and comprehensive view of network traffic.

[0319] The Meta-Policy Model

[0320] According to the preferred embodiment of the invention, the meta-policy object 601 is an object-based representation or model of a network security policy, and is the underpinnings of the policy specification abstraction that the policy developer studio presents users.

[0321] A table of definitions of terminology used in describing the claimed invention is provided below in Table S.

TABLE S
A “Meta-policy” comprises a collection of “Network Objects”, a collection of “Services”,
a collection of “Relationships”, and a collection of “Outcomes”;
A Network Object comprises IP-addresses, containment of other Network Objects, an
attribute of Reporting Element, and an attribute of Owner;
The attribute Reporting Element is a Boolean value. At times the term “Reporting
Element” is used to represent a Network Object that has its Reporting Element
attribute set to true;
The attribute Owner is a String and is always optional. It represents an entity, such as
a person or organizational role, which should be informed of any anomalous network
traffic involving the Network Object. If a network object does not explicitly identify an
owner, its owner is that of its nearest containing network object where an owner has
been specified, if any;
IP-addresses can be a single IP-address, a list of IP-addresses, a range of IP-
addresses, or an IP-mask;
A Network Object is any of a:
Host
Host Group;
Network Interface;
Perimeter Element;
Subnet;
Top-Level-Network; and
Identity Object
A Host represents a machine on a network;
A Host Group represents one or more Hosts. It consists of zero or more IP-addresses
and may contain zero or more other Host Group objects;
A Network Interface is a Network Object with only a single IP-address and a single
MAC-address. (Has no containment of other Network Objects). It also has a reference
to a single Perimeter Element, and a single Subnet;
A Perimeter Element is a Network Object that contains all of the Network Interfaces
that connect it to subnets. (Has no IP-addresses). A Perimeter Element represents
both routers and firewalls;
A Subnet is a network object that contains one or more IP-addresses in the form of IP-
masks. (Has no explicit containment of other network objects). Subnets have
attributes of: Subnet Type, and Monitor Point;
The attribute Subnet Type is the enumeration of “Intranet” and “Extranet”;
The attribute Monitor Point is a Boolean value. The term “Monitored Subnet” is used to
describe a Subnet Object that has Monitor Point attribute of true. A Subnet that is
marked as Monitored represents a collection point for traffic in a network;
Top-Level-Networks has the instances “Intranet”, “Extranet”, “Internet” and “All
Networks”;
The Intranet and Extranet Top-Level-Networks explicitly contain subnets marked with
the appropriate subnet type;
All Network Objects that could be contained in a Subnet that are not implicitly
contained in a Subnet Object are implicitly contained within the Top-Level-Network
“Internet”;
The “All Networks” Top-Level-Network explicitly contains the Top-Level-Networks
“Intranet”, “Extranet” and “Internet”;
An Identity Object is any of a user, computer, and Identity Group:
A user is an authenticated human user or a computer process;
A computer is an authenticated machine or Host; and
An identity group represents a collection of other identity group, or computers;
A Network Object can implicitly contain other Network Objects by IP-address, e.g. a
Host is contained in a Subnet by having an IP-address that matches the IP-mask of the
subnet. The implicit containment rules for Network Objects are as follows:
Host Groups may contain other Host Groups; Host Groups may contain
Network Interfaces; and
Subnets may contain Host Groups and Network Interfaces;
A Network Object that is a Reporting Element must be a proper subset of any other
Network Object that is also a Reporting Element;
A Relationship contains two Network Objects (Initiator and Target), a single Service
and a single Outcome. The Protocol of the Relationship's Outcome must match the
Protocol of the Relationship's Service;
A Service is made up of zero or more Ports (expressed as Integers between 0 and
65535); one or more Protocols; and an Owner;
An Outcome is made up of a Protocol; an Owner; and an associative array of
“Components” to “Criticality”;
A Criticality is an enumeration. (“OK”, “MONITOR”, “WARNING”, “MEDIUM”, “HIGH”,
“CRITICAL”);
A Component is made up of a Condition and collection of Protocol Actions;
A Condition is a condition as defined in the Policy Language (FIG. 1 108) along with the
value of the condition;
A Protocol Action is an action as defined in the Policy Language (FIG. 1 108);
A Network Topology represents a logical view of a network. It consists of the series of
Subnets connected together via Perimeter Elements;
An XNet is the set of Network Objects that include the Top-Level-Network objects
“Intranet”, “Internet”, “Extranet” and the Current Monitored Subnet if the network object
is in a Monitored Subnet;
An Offered Service of a Network Object is a Service that is in a Relationship in which
the Network Object is the target;
NAT (Network Address Translation) is a procedure by which a router or firewall
changes data in packets to modify the network address;
Depth First Search is a search algorithm that considers outgoing edges of a node's
before any neighbors of the node, that is, outgoing edges of the node's predecessor in
the search. Extremes are searched first; and
Breadth First Search is a search algorithm that considers neighbors of a node, that is,
outgoing edges of the vertex's predecessor in the search, before any outgoing edges
of the node. Extremes are searched last.

[0322] The preferred embodiment of the meta-policy object-based representation of a network security policy is described with reference to FIG. 7. FIG. 7 is a schematic diagram of meta-policy objects and their associations according to the invention. At the center of the diagram is a meta-policy 601. Solid lines without arrows represent associations and/or containments. A zero with two dots and a star following means zero or more. Likewise, a one with two dots and a star following means one or more. An arrow at the end of a line represents that each object below the arrow is a type of the object to which the arrow points.

[0323] Therefore, referring to FIG. 7, a meta-policy 601 is associated with zero or more outcomes 701, with zero or more relationships 702, with zero or more network objects 703, and with zero or more services 704. A network object 703 can contain other network objects by implicit or explicit containment 705. A network interface 706, a host group 707, a top level network 708, a subnet 709, and a perimeter element 710 are each a type of network object 703. Therefore, whatever applies to network objects necessarily applies to each of such network object types. A network object 703 is associated with only one meta-policy 601. The relationship 702 is associated with only one service 704, and, similarly, is associated with only one outcome 701. The relationship, however, is associated with two network objects, namely, initiator and target. An outcome 701 contains one or more components 711, and each component 711 is associated with one criticality 712.

[0324] It should be appreciated that from such meta-policy objects, policy language objects described herein above are generated in a natural way (FIG. 6 602b). A detailed description of such generation follows.

[0325] Generating Policy from Meta-Policy

[0326] The following sections below, namely, Generation of Route Information, Generation of Host Information, Generation of Subnet Credentials, Generation of Host Group Credentials, Generation of Perimeter Element Credentials, Generation of NAT Credential/Information, Generation of Rules from Relationships, Rules Describing a Relationship, and Reporting of Services by Reporting Elements (XNet Rules), describe how policy language objects cited herein above are generated from the claimed meta-policy objects according to the preferred embodiment of the invention. It should be appreciated that variations of the generation of policy from meta-policy are possible, still being within the scope of the claimed invention, and that the following teachings are meant to be illustrative and not exclusive.

[0327] Generation of Route Information

[0328] For each monitored subnet create an associative array, i.e. routes, where the key is a unique pair of network interfaces on such subnet and the value is a collection of pairs of subnets whose traffic flows between such network interfaces.

[0329] Table T below provides an example of pseudo code for generating route information according to the preferred embodiment of the invention. Referring to such pseudo code, route information is generated by doing a modified depth first search of a given network topology. For each subnet visited by the depth-first search, i.e., a visited subnet, only the routes between the starting subnet and another subnet are maintained. It should be appreciated that a list of routes, i.e. the route list, comprises a collection of pairs of interfaces, whereby each pair of interfaces represents a particular flow across a visited subnet.

TABLE T
For each net in all Subnets
generateRoutes(net, net, null, new List( ))
End foreach
proc generateRoutes(Subnet startSubnet, Subnet currentSubnet,
NetworkInterface inInterface, List route)
for each pair of Network Interfaces in route except the first
// NOTE: exception is due to the first entry having a null inInterface
Subnet net = subnet between the two interfaces
net.route{key=network interface pair}.add(first=startSubnet,
second=currentSubnet)
end for
for each outInterface in currentSubnet.networkInterfaces do
if outInterface != inInterface then
route.add( first = inInterface, second = outInterface )
for each farInterface in
outInterface.perimeterElement.networkInterfaces
Subnet farSubnet = farInterface.subnet
if route does not have farSubnet between the two interfaces then
generateRoutes(startSubnet, farSubnet, farInterface, route)
end if
end for
route.removeLast
end if
end for
end generateRoutes

[0330] For each element in the “routes” collection create a rule allowing the complete set of potential IP traffic between the originating and terminating network interfaces.

[0331] Generation of Host Information

[0332] For each subnet object, create an associative array, referred to as hosts, wherein the key is a network object that is partly or wholly contained within the particular subnet, referred to as implicit containment, and the value is the subset of the IP-addresses of such network object that are contained within the subnet.

[0333] Generation of Subnet Credentials

[0334] For each subnet object create a credential which has an “or” assertion containing the IP-masks and the host credentials of the values of the hosts associative array.

[0335] Create a group with a type of “agent_attr_t”, comprising a union of the names of all of the subnets that are marked as monitoring points.

[0336] For each monitored subnet create a credential comprising a “member” assertion of the subnet name and “agent-attribute”.

[0337] Create a credential for Intranet which has an “or” assertion made up of the credentials of all the subnets marked as “Intranet”.

[0338] Create a credential for Extranet which has an “or” assertion made up of the credentials of all the subnets marked as “Extranet”.

[0339] Create a credential for Internet which has the assertion of “not” of the “or” of the “Intranet” and “Extranet” credentials, and Illegal IP-addresses.

[0340] Generation of Host Group Credentials

[0341] For each host group object create a credential with the “or” assertion of all of the IP-addresses of the host group and the credentials of any host groups it contains.

[0342] Generation of Network Interface Credentials

[0343] For each network interface object create a credential with the IP-address of the network interface, referred to as the network interface IP-address credential, another credential with the MAC-address of the network interface, referred to as the network interface MAC-address credential, and a third credential with the “and” assertion of the first and second aforementioned credentials.

[0344] Generation of Perimeter Element Credentials

[0345] For each perimeter element object create a credential with the “or” assertion of all of the IP-address credentials of the. network interfaces attached to the given perimeter element.

[0346] Generation of NAT Credential/Information

[0347] For each monitored subnet object create an associative NAT array wherein the key is a network object and the value is a credential depicting how the network object would appear on the monitored subnet, i.e. the NAT credential. Create an entry for each network object in the system.

[0348] To calculate the NAT credential, find all paths from the monitored subnet to the subnets where the network object can be found. For each path apply any NAT supplied by all of the network interfaces along the path from the monitored subnet to the subnets where the network object resides. If no NAT is applied to the network object, then use the credential of the network object. If NAT is applied by one or more paths, then create a credential with an “or” assertion of the IP-addresses applied by each of the paths.

[0349] Generation of Rules from Relationships

[0350] For each monitored subnet object, find all of the relationship objects that define traffic visible from the monitored subnet. In so doing, consider all relationships associated with each network object. Furthermore, in the case when the network object is a reporting element, consider also the relationships of other network objects that implicitly or explicitly contain this network object. For each relationship create a set of rules that describe the traffic allowed for the relationship on the monitored subnet.

[0351] To find the initiator and target credentials, use the value of the NAT associative array for the monitored subnet using the initiator and target values of the relationship.

[0352] If the service object contains initiator or target ports, then create a credential with the assertion of “and” combining the initiator/target credential with a credential describing the ports of the service.

[0353] Generating Rules Per Outcome Component

[0354] Using the outcome object, create an associative array, referred to as actions, wherein the key is a protocol action and the value is an associative array whose key is a condition and whose value is a criticality. The actions associative array has an entry for each action defined by the protocol to which the outcome object pertains.

[0355] Optimization step: For each action of the actions array, combine actions that have the same value.

[0356] For each key in the actions associative array, create a rule for the protocol represented by the outcome, listing all protocol actions given by such key. In the outcome section of such rule, create a guarded clause for each of the conditions given by the value of the actions associative array's entry. Each guarded clause, as well as the default clause, emits a disposition whose name comprises the owner, if any, the outcome component, i.e., the condition in the guarded clause, and the outcome component's criticality. The latter is also reflected in the disposition's severity.

[0357] The owner is determined first by selecting the owner of the outcome. If the owner of the outcome does not exist, then the selected owner is the owner of the service if it exists. If the owner of the service does not exist, the owner is the owner of the target reporting element if it exists. If the owner of the reporting element does not exist, an owner is not assigned to the relationship's dispositions.

[0358] Reporting of Services by Reporting Elements (XNet Rules)

[0359] To classify traffic for a reporting element for traffic analysis or for network assessment, perform the following steps:

[0360] For each network object that is a reporting element, create a set of rules for each offered service of such network object, whether an explicit offered service or an inherited offered service from a containing network object, that describe inbound traffic as originating from an unexpected host. There is one such rule for each XNet, thus identifying the offending client as a member of that XNet.

[0361] Each of such rules issues a disposition that includes the owner of the traffic, if an owner can be determined. The owner is determined first by selecting the owner of the service. If the owner of the service does not exist, then the selected owner is the owner of the reporting element, if one exists, or none if it does not exist.

[0362] Optimization step: Group the services by the owners of the service and use the group of services by owners as the “or” of the group of services having the same owners when generating the target credential.

[0363] For each network object that is a reporting element, create a set of rules that classify traffic, such as, for example, TCP, UDP, or ICMP, and either inbound or outbound, using each of the XNets as the initiator (inbound) or target (outbound) and the network object as the target (inbound) or initiator (outbound), respectively.

[0364] An Exemplary Policy Developer Application User Interface

[0365] The preferred embodiment of the policy developer system provides a graphical user interface, the policy developer GUI, to the meta-policy. Such policy developer GUI comprises, but is not limited to, the following features for implementing the means for providing an interface to the meta-policy objects for manipulation for creating a desired policy. Details about each feature are provided in the sections below of the same name. The main features of the preferred embodiment are listed below and can be understood with reference to FIG. 8, wherein FIG. 8 is an example of a GUI window showing the main features of the policy developer GUI according to the invention:

• • [0366] An application menu bar 801;
  • [0367] Toolbars 802;
  • [0368] A subnet pane 803;
  • [0369] A tabbed content pane 804;
  • [0370] A tabbed messages pane 805; and
  • [0371] Various property windows used to define the objects within a given policy.

[0372] It should be appreciated that such features above are by example only and not meant to be an exclusive, and that various embodiments of the policy developer GUI are within scope of the invention.

[0373] Application Menu Bar

[0374] The preferred embodiment of the invention provides a policy developer GUI application menu bar 801 comprising, but not limited to, the following options:

• • [0375] File, for accessing file manipulation functions;
  • [0376] Edit, for editing a policy;
  • [0377] Run, for running a policy;
  • [0378] Subnet, for adding components to a subnet pane;
  • [0379] Policy, for manipulating a policy;
  • [0380] Window, for bringing currently open application windows to the foreground; and
  • [0381] Help, for providing help on the policy developer GUI application.

[0382] In the preferred embodiment of the invention, the file menu provides standard file manipulation options such as, for example:

• • [0383] new, for creating a new and empty policy and containing only the definition of “All Other Hosts”;
  • [0384] open, for opening an existing policy;
  • [0385] save, for saving the current policy using its existing name;
  • [0386] save as, for saving the policy to a new file and directory, wherein the default filename is the policy name with the extension, .pdx;
  • [0387] print, for printing a view of the current active window, and
  • [0388] exit, for exiting the policy developer GUI application with standard exit options, such as, for example, yes, no, and cancel.

[0389] The edit menu option in the preferred embodiment of the invention provides, but is not limited to standard edit options, such as, for example: undo, copy, cut, and paste.

[0390] The run menu comprises, but is not limited to, an evaluate policy option, whereby upon selection, the current policy is evaluated against a particular network traffic file. The preferred embodiment of the evaluate policy option can be described in further detail by reference to FIG. 9. FIG. 9 is an example GUI window for the evaluate policy option according to the invention. The evaluate policy option gathers and provides the following information, respectively:

• • [0391] Filestore name, for specifying the name of the repository that the policy engine (FIG. 1 101) uses for output data;
  • [0392] User name, for specifying a user name used to identify the user of the filestore;
  • [0393] Password, for specifying a password used to authenticate the user of the filestore;
  • [0394] DMP/DME file, for specifying the name of the network traffic file to be evaluated by the policy;
  • [0395] Collection point, for specifying the point within the network where data contained in the network traffic file was collected;
  • [0396] Log, for specifying whether or not to log information about all traffic or only traffic that violated the policy;
  • [0397] Start/Stop buttons, for controlling the operation of the policy engine 101, wherein the start option processes the policy file for evaluation, and wherein the stop option cancels processing by the policy engine 101; and
  • [0398] An Output pane, for displaying output from the policy engine 101 as it performs policy evaluation.

[0399] The subnet menu comprises, but is not limited to the following options according to the preferred embodiment of the invention:

• • [0400] Subnet, for creating a new subnet that appears in the desired location within the subnet pane;
  • [0401] Firewall, for creating a new firewall object that appears in the desired location within the subnet pane;
  • [0402] Router, for creating a new router object that appears in the desired location within the subnet pane;
  • [0403] Internet, for representing the Internet; and
  • [0404] Connect, for creating a new connection between a subnet object and a firewall or a router object, as well as between the Internet object and a firewall or a router object.

[0405] The policy menu comprises, but is not limited to the following options according to the preferred embodiment of the invention:

• • [0406] New host, for creating a new host object and for providing a means for specifying host properties, such as, for example, a host properties window;
  • [0407] New service, for creating a new service object and for providing a means for specifying service properties, such as, for example, a service properties window;
  • [0408] Compile, for generating a form of the policy suitable for the policy engine 101 and having the file extension, .spm; and
  • [0409] Generate policy description, for generating a human readable policy description document for the current policy, and wherein once processing is complete, the messages pane thus preferable contains a policy description tab that itself contains the name of file that was created, such as, for example, the root HTML file.

[0410] It should be appreciated that the compile feature is used implicitly and automatically when the run > evaluate policy option is used. The explicit specification of compile may be useful when fixing compilation errors and warnings, for example.

[0411] The window menu brings specified windows to the front, such as, for example:

• • [0412] Messages, for bringing the messages window to the front; and
  • [0413] Subnet, for bringing the subnet window to the front.

[0414] The help menu comprises, but is not limited to an about option for displaying the standard about information.

[0415] Toolbars

[0416] The preferred embodiment of the invention provides an applications toolbar and a subnet toolbar 802. The application toolbar provides, but is not limited to, easy access to commands available in the file menu and the policy menu described above. The subnet toolbar provides easy access to commands available in the subnet menu herein above. FIG. 10 shows an example of a subnet toolbar having subnet icons and functions according to the preferred embodiment of the invention.

[0417] Subnet Pane

[0418] The preferred embodiment of the invention provides a policy developer GUI subnet pane 803 that is used to define from a monitoring point of view the topology of the network. Such view is a simplified view of the network as compared to the typical contemporary network diagram. The subnet pane naturally allows interest in subnet addresses and network address translation (NAT) in the vicinity of the subnets desired to be monitored. FIG. 11 is an example of a subnet pane comprising a plurality of firewall, subnet, and connection objects according to the invention.

[0419] An advantage of adding specific details to the subnet diagram, such as depicted in FIG. 11, for example, is that such added details allow the policy to monitor the correctness of the IP routing configuration on the monitored networks. Included in such monitoring of correctness of the IP routine is the monitoring of traffic that traverses a monitored net across routers and firewalls that are performing NAT.

[0420] Icons on the subnet diagram, such as depicted in FIG. 11, may be selected and dragged to improve the aesthetics of the diagram. While an icon is dragged, its connections to other components are maintained.

[0421] Each icon has an associated properties window. For example, a properties window of the component for the particular icon can be opened by double-clicking on such icon. The components of the subnet pane are listed and described in further detail below and referring to FIG. 11:

• • [0422] Internet object, for representing all subnets not explicitly defined within the current policy, and, therefore, is the only Internet object per subnet diagram;
  • [0423] Subnet object, for representing a collection of IP subnets. The following information about the subnet object is displayed, preferably on the subnet object icon: the name of the subnet block, the masks of the subnets within such block, and a magnifying glass icon indicating whether such subnet block contains a monitoring point;
  • [0424] Router object, for representing a routing element within a network. Contained within the icon is the name of the router and a “T” icon indicating whether such router performs NAT;
  • [0425] Firewall object, for representing a firewall element within a network. Contained within the icon is the name of the firewall and a “T” icon indicating whether such firewall performs NAT;
  • [0426] Connection, for indicating that it is possible for traffic to flow between a perimeter element, such as a router or firewall, and a subnet block. Creating a connection between a perimeter element and a subnet block causes a network interface to be added to the perimeter element; and
  • [0427] Network interface object, for representing a logical interface on a router or firewall, such label containing the name of the interface.

[0428] It should be appreciated that the router icon is equivalent to the firewall icon and vice-versa.

[0429] Tabbed Messages Pane

[0430] The preferred embodiment of the invention provides a tabbed messages pane for displaying messages, preferably text messages, such pane being clearable either by choice by a user or automatically by the GUI application. The tabbed messages pane is described with reference to FIG. 12. FIG. 12 is a screen shot of an example messages pane in a window according to the invention. The preferred embodiment of the invention provides a console tab and a compiler tab (FIG. 12). The console tab displays informational text messages that are output from the policy developer GUI application. The compiler tab displays output from the policy compilation process, comprising, but not limited to warnings and errors, such warnings and errors preferably provided in a corresponding list of compiler warnings and errors.

[0431] An equally preferred embodiment of the invention provides a policy description tab for displaying output from the policy description generation process and is described with reference to FIG. 13. FIG. 13 is a screen shot of an example policy description tabbed messages pane according to the invention. Included in, but not limited to, the output is the location of the created file, such as, for example a top level HTML file. Such policy description messages window is cleared each time the generate policy description option is selected.

[0432] Tabbed Content Pane

[0433] The preferred embodiment of the invention provides a tabbed content pane for listing all the objects that are available within the current policy. Such content pane contains, but is not limited to three tabs: hosts, services, and outcomes. Each object in the content pane is linkable to an associated properties dialog.

[0434] Hosts Tab

[0435] The preferred embodiment of the hosts tab is described with reference to FIG. 14a. FIG. 14a is a screen shot of a view of an example hosts tab display according to the invention. Such hosts tab provides a detailed listing of the following categories of objects contained in the current policy:

• • [0436] All networks;
  • [0437] Internet;
  • [0438] Extranets;
  • [0439] Intranets;
  • [0440] Subnets;
  • [0441] Hosts; and
  • [0442] Perimeter elements.

[0443] Each of such categories above nests other components that are logically contained within them. For example, the “Application Server Layer” subnet contains the Logging Server because the latter's IP address (10.59.179.101) is contained within the former's IP mask (10.59.179.0/24). This is termed implicit containment. Objects that are reporting elements are depicted as such, such as in bold text. Deleting an object from the list deletes the object from the current policy and from all relationships within such policy in which it currently takes part.

[0444] An equally preferred embodiment of the invention provides means for a network object in the hosts tab to transfer, preferably by drag-and-drop, into a To or From field of a Requiring or Offering tabs of the Internet, Subnet, Host, or Network Interface property dialogs described herein below.

[0445] Services Tab

[0446] The preferred embodiment of the services tab is described with reference to FIG. 14b. FIG. 14b is a screen shot of a view of an example services tab display according to the invention. Such services tab provides a listing of all services defined within the current policy. The entry in the services tab display represents:

• • [0447] The service name, e.g. Https;
  • [0448] The base protocol used by the service, e.g. ssl in “Https (ssl: ...”; and
  • [0449] The IP ports used by the service e.g. tcp ports 443 in “Https (ssl: tcp/443)”.

[0450] It should be appreciated that not all services defined in the services tab are necessarily currently in use in the current policy, but are simply available for use. Deleting a service from the list deletes the service from the current policy and from all relationships within such policy in which it is used.

[0451] An equally preferred embodiment of the invention provides means for a service name in the services tab to transfer, preferably by drag-and-drop, into the Service field of the Requiring or Offering tabs of the Internet, Subnet, Host, or Network Interface property dialogs described herein below.

[0452] Outcomes Tab

[0453] The preferred embodiment of the outcomes tab is described with reference to FIG. 14c. FIG. 14c is a screen shot of a view of an example outcomes tab display according to the invention. Such outcomes tab provides a detailed listing of all outcomes defined within the current policy. An outcome creates a named set of criticalities that may be assigned to particular types of interactions between network entities. Because the interactions that can occur vary depending on the service being used, outcomes are defined in the context of particular services. Deleting an object from the list deletes the outcome from the current policy provided the outcome is not currently in use.

[0454] The preferred embodiment provides means for creating an outcome for a current service, for example, by double-clicking on an outcome icon folder to open the associated properties dialog. An existing outcome can be edited, for example, by double-clicking on an outcome name to open the associated properties dialog.

[0455] An equally preferred embodiment of the invention provides means for outcome names in the outcomes tab to transfer, preferably by drag-and-drop, into the outcomes field of the Requiring or Offering tabs of the Internet, Subnet, Host, or Network Interface property dialogs described herein below.

[0456] Various Property Windows Used to Define the Objects within a Given Policy

[0457] The preferred embodiment of the invention provides means for displaying meta-policy object properties, preferably in windows or dialogs, and wherein some or all properties of a current object may be editable. Following is a list of provided properties windows according to the preferred embodiment of the invention. Clearly, such list is meant as by example only and is not meant to be exclusive:

• • [0458] Subnet properties;
  • [0459] Host group properties;
  • [0460] Perimeter element properties;
  • [0461] Network interface properties;
  • [0462] Top-level networks properties;
  • [0463] Service properties; and
  • [0464] Outcome properties.

[0465] Subnet Properties

[0466] Table U below describes the specified subnet properties and the meanings and/or indications of such according to the preferred embodiment of the invention. FIG. 15 is a screen shot of an example subnet properties dialog according to the invention.

TABLE U
Property	How to select	What it means
Name	Click in edit area.	This name is used to describe traffic
		to and from the subnet.
Subnet Type	Click on selection	Subnets may be classified as
	tab.	“Intranet”
		“Extranet”
		This classification changes the color
		of the subnet in the Subnet diagram
		and the nesting of the subnet under
		“Intranet” or “Extranet” in the Hosts window.
Collection	Check to enable.	Indicates that it is intended to
Point		capture packet data on the subnet,
		including intra-subnet traffic. A
		subnet object containing a Collection
		Point is denoted with a magnifying
		glass icon. Policy Evaluation
		requires that at least one subnet
		have a Collection Point.
Collection	Click in edit area when	Set a symbolic name to identify the
Point name	Collection Point is	collection point. When evaluating
	checked.	policy, this string must be supplied to
		identify the source of packet capture
		data. When continuous monitoring of
		policy is in place, the monitor is
		configured with the correct collection
		point name.
Reporting	Check to enable.	Determines whether or not policy
Element		developer application should
		generate reports on all traffic to and
		from this subnet. If traffic is not
		covered by a reporting element, the
		policy classifies it as “Unreported”
		and declares it to be “OK”. A subnet
		that is a reporting element appears in
		bold in the Content Pane.
Reporting Element	Click in edit area when	The text field to the right of the
Owner	reporting element is	Reporting
	checked.	Element checkbox. A string
		describing the Group or person
		responsible for maintaining this
		Reporting element.
Generate	Check to enable.	Generate a highly granular policy
Discovery		that categorizes traffic to and from
Policy		this subnet by service categories.
Masks tab	Click on Masks tab.	IP Masks that define this subnet or
		subnet collection.
Requiring tab	Click on Requiring tab.	Relationships that apply to all hosts
		in this subnet.
Offering tab	Click on Offering tab.	Relationships that apply to all hosts
		in this subnet.

[0467] Host Group Properties

[0468] Table V below describes the specified host group properties and the meanings and/or indications of such according to the preferred embodiment of the invention. FIG. 16 is a screen shot of an example host group properties dialog according to the invention.

TABLE V
Property	How to select	What it means
Name	Click in edit area.	The name of the Host Group. This name is
		used to describe traffic to and from the Host
		Group.
Button icon	Click button.	Closes the current Host Group properties
		window and creates a new Host Group object.
Reporting	Check to enable.	Determines whether or not the policy developer
Element		application should generate reports on all traffic
		to and from this Host Group. If traffic is not
		covered by a reporting element, the policy
		classifies it as “Unreported” and declares it to
		be “OK”. A Host Group that is a reporting
		element appears in bold in the Content Pane.
Reporting	Click in edit area	The text field to the right of the Reporting
Element owner	when reporting	Element checkbox. A string describing the
	element is	group or person responsible for maintaining
	checked.	this reporting element.
Generate	Check to enable.	Generate a highly granular policy that
Discovery Policy		Categorizes traffic to and from this Host Group
		by service categories.
Addresses tab	Click on	IP-Addresses, -masks, -ranges or network
	Addresses tab.	object names that correspond to network
		objects contained within this Host Group.
Notes tab	Click on Notes	Text notes about this Host Group.
	tab.
Requiring tab	Click on Requiring	Relationships that apply to all hosts in this Host
	tab.	Group.
Offering tab	Click on Offering	Relationships that apply to all hosts in this Host
	tab.	Group.

[0469] Perimeter Element Properties

[0470] Table W below describes the specified perimeter element properties and the meanings and/or indications of such according to the preferred embodiment of the invention. FIG. 17 is a screen shot of an example perimeter element properties dialog according to the invention.

TABLE W
Property	How to select	What it means
Name	Click in edit area.	The name of the perimeter
		element. This name is used
		to describe traffic to and
		from the perimeter element,
		as well as traffic that
		transits through the
		perimeter element.
Does IP Address	Select Yes or No radio	Defines whether this
Translation?	button.	perimeter element's
		network interfaces support
		NAT.

[0471] Network Interface Properties

[0472] Table X below describes the specified network interface properties and the meanings and/or indications of such according to the preferred embodiment of the invention. FIG. 18 is a screen shot of an example network interface properties dialog according to the invention.

TABLE X
Property	How to select	What it means
Name	Click in edit area.	The name of the interface. This name
		is used to describe traffic to and from
		the network interface, as well as traffic
		that transits through the interface.
Reporting	Check to enable.	Determines whether the policy should
Element		generate reports on all traffic to and from this
		interface.
Reporting	Click in edit area when	The text field to the right of the
Element owner	reporting element is	Reporting Element checkbox. A string
	checked.	describing the group or person
		responsible for maintaining this
		reporting element.
MAC	Click in edit area. Enter	The machine address of the interface.
	as 6 hex bytes	This is also sometimes called the
	separated by ‘-’ or ‘:’.	Ethernet address. The MAC address
		of the router interface is used during
		policy evaluation to check for rogue
		routers and other topology violations.
IP Address	Click in edit area.	The IP address associated with this
		network interface. This is needed only
		if the router sends or receives data on
		the network as if it were a regular host.
NAT tab	Click on tab.	Many routers and firewalls perform
		Network Address Translation (NAT). In
		NAT, the router translates addresses
		as data passes through it. This is
		commonly done so that the true
		addresses of hosts are not visible on
		the Internet, although other
		configurations are possible.
		NAT is configured for the interface
		towards which the translation occurs.
		For example: If all addresses inside the
		network map to one address on the
		outside, NAT is configured on the
		outside interface of the router. If all
		addresses in the Internet map to one
		address on the inside of the network,
		NAT is configured on the inside
		interface of the router.
		The most common case is to configure
		NAT only on the outside interface of
		the router.
Requiring tab	Click on Requiring tab.	Relationships between this perimeter
		element (acting as a host), through this
		interface, and other network objects.
Offering tab	Click on Offering tab.	Relationships between this perimeter
		element (acting as a host), through this
		interface, and other network objects.

[0473] Top-Level Networks Properties

[0474] Table Y below describes the specified top-level networks properties and the meanings and/or indications of such according to the preferred embodiment of the invention. FIG. 19 is a screen shot of an example top-level networks properties dialog according to the invention.

TABLE Y
Property	How to select	What it means
Name	Not selectable.	The name of the Top Level Network
		object.
Reporting	Check to enable.	Determines whether or not the policy
Element		developer application should generate
		reports on all traffic to and from this
		Top Level Network. If traffic is not
		covered by a reporting element, the
		policy classifies it as “Unreported” and
		declares it to be “OK”. A Top Level
		Network that is a reporting element
		appears in bold in the Content Pane.
Reporting	Click in edit area	The text field to the right of the
Element	when reporting	Reporting Element checkbox. A string
owner	element is checked.	describing the group or person
		responsible for maintaining this
		reporting element..
Generate	Check to enable.	Generate a highly granular policy that
Discovery		categorizes traffic to and from this Top
Policy		Level Network by service categories.
Requiring	Click on Requiring	Relationships that apply to all hosts
tab	tab.	implicitly contained in this Top Level
		Network.
Offering	Click on Offering	Relationships that apply to all hosts
tab	tab.	implicitly contained in this Top Level
		Network.

[0475] Service Properties

[0476] Table Z below describes the specified service properties and the meanings and/or indications of such according to the preferred embodiment of the invention. FIG. 20 is a screen shot of an example service properties dialog according to the invention.

TABLE Z
Property	How to select	What it means
Name	Click in edit area.	The name of the service.
Services	Click button.	Close the current Service and create a
icon		new Service object.
Owner	Click in edit area to	A string describing the owner of the
	create new owner;	service. This is an optional field. It is
	Select previous	used in policy evaluation to identify a
	entered	person or group that should be notified
	owner from list.	whenever an outcome pertaining to this
		service occurs. Note, however, that an
		outcome owner takes precedence over
		a service owner.
Base	Choose from list.	Choose which base service this new
Protocol		service builds upon. The value
		selected here directly correlates to the
		particular Outcomes that are available
		to this service.
Outcome	Choose from list.	Defines the Outcome that will be
		applied to Unexpected traffic using this
		service when the Discovery Policy is in
		use.
Traffic	Not selectable.	Defines how traffic for this service
Descriptor		appears on the network.
Protocol	Choose from list.	Select the base protocol for which you
Layers		are currently configuring port numbers.
		Note that multiple base protocols are
		only selectable for Services using both
		TCP and UDP protocols.
Initiators	Click in edit area.	The expected source port when this
		service uses the current Protocol
		Layer. Empty if any port may be used.
		Multiple ports may be specified.
Targets	Click in edit area.	The expected destination port when
		this service uses the current Protocol
		Layer. Empty if any port may be used.
		Multiple ports may be specified.

[0477] Outcome Properties

[0478] Table AA below describes the specified outcome properties and the meanings and/or indications of such according to the preferred embodiment of the invention. FIG. 21a is a screen shot of an example outcome properties dialog according to the invention.

TABLE AA
Property	How to select	What it means
Name	Click in edit area.	The name of the outcome that appears
		in the relationship description.
Outcome	Click button.	Close the current outcome and create
icon		a new Outcome object.
Owner	Click in edit area	A string describing the owner of the
	to create new	outcome. This is an optional field. It is
	owner; Select	used in policy evaluation to identify a
	previous owner	person or group that should be notified
	from list.	whenever this outcome occurs.
Component	Not selectable.	Describes a list of circumstances that
		may be configured to have different
		criticality. This component will vary
		depending on the base protocol to
		which this Outcome may be applied.
		FIG. 21 provides representative
		examples of applicable outcome
		components for the HTTP (FIG. 21a),
		IP (FIG. 21b) and UDP (FIG. 21c)
		protocols.
Criticality	Choose from list.	Selects a particular criticality level for a
		Component.

[0479] An Exemplary Policy Description Document

[0480] The preferred embodiment of the invention provides a system and method for generating a policy description document from the meta-policy primarily for, but not limited to, the following reasons:

• • [0481] It is desirable that the complex interdependencies of network objects, such as, for example, host groups, network interfaces, perimeter elements, subnets, and top-level networks as used within and described by a current network security policy to render a human-readable representation of the policy;
  • [0482] It is desirable that a human-readable policy description be compiled from a particular meta-policy representing a current network security policy into a single, multi-page, hyper-linked document, or, in the case of a published web site, multiple documents referencing each other as a single logical document. Such policy description format facilitates the sharing of network security policy with other entities without requiring that access be granted to proprietary information; and
  • [0483] It is desirable to provide means for quick comprehension of policy engine output information comprising annotating, either manually or automatically, such policy engine output information to a policy description document, thereby allowing a user to reference the associated network traffic in the greater context of the current policy domain.

[0484] The preferred embodiment of the invention comprises, but is by no means limited to the following primary elements, described in further detail in sections of the same name describing methodology for their respective generation.

• • [0485] Overview indexes by name and by network listing all of the network objects described within the current network security policy, i.e. the policy domain;
  • [0486] Network object pages comprising the details of the services and relationships, generated manually and/or procedurally between other network objects; and
  • [0487] An outcomes page showing each criticality assigned to associated relationship outcomes.

[0488] Generating a Policy Description Document from Meta-Policy

[0489] Following is a methodology for generating a policy description document from meta-policy according to the preferred embodiment of the invention.

[0490] Generation of Name Indexes and Network Indexes

[0491] The preferred embodiment of the policy description document provides an overview, thereby also rendering the policy description document to be scalable. Experience has shown that two preferred indexes are all network objects by name and all network objects by network hierarchy, the preferred embodiments of which are described below.

[0492] Indexing by name, referred to herein as “By Name,” means listing all network objects in ascending order by leading character of its name along with each network object's associated IP addresses, subnet masks, contained host groups, or other unique identifiers. Indexing by network hierarchy, referred to herein as “By Network,” means listing all networks to which the current policy speaks, in the fashion made familiar to the user through the interactive interface of the Policy Developer Studio, i.e. in the order determined by the containment hierarchy.

[0493] A network interface is listed beneath the associated perimeter element to which it belongs, although such interface assigned to a perimeter element is itself considered a discrete network object. Listed with each interface is its associated IP and MAC addresses.

[0494] Each entry in such indexes is a hyperlink to a corresponding network objects page describing that specific network object. Network objects that are reporting elements are presented in a distinctive manner or type, such as, for example, in boldface type.

[0495] It is preferable that a user can simply switch between these two index views because different views may be desired for different types of research. To that end, IP addresses preferably are hyperlinks to the opposing index.

[0496] Additionally, the preferred embodiment of the invention provides hyperlinks at the top of both index pages to the outcome page.

[0497] Generation of Network Object Pages

[0498] A description of the preferred embodiment of the generation of a network object page follows. A network object page contains all pertinent information specific to such network object. The network object page includes, but is not limited to, relationships in which the network object is involved. The network object page also includes the outcomes of such relationships. Therefore, the network object page illustrates all possible relationships granted a particular network object, either directly or as a result of the network object's implicit or explicit containment within other network objects. The network object's relationships are listed in order, starting with those defined for the network object itself, followed by those defined by its nearest containing network object, recursively.

[0499] Network Object Page Headings

[0500] In the preferred embodiment of the invention, the heading of the network object page contains in order of the page's visual hierarchy: the object's name, a hyperlink to its entry on the “By Network” index page, and a list of hyperlinks to object pages of the network objects in which it is contained.

[0501] One exception to the discussed network object page heading format above is the format for network interfaces of perimeter elements. Interfaces are named with their enclosing perimeter element as a prefix, such as, for example, in “[perimeterElement_—1]_[interfaceName],” because an interface is part of a perimeter element.

[0502] Network Object Page Bodies

[0503] The preferred embodiment of the invention provides the body of a network object page that lists all services that such network object offers and requires, and lists other network objects with which the particular network object has such offering and requiring relationships. It should be appreciated that a network object noted in a page body is a hyperlink to the corresponding network object page, similarly to such network objects noted in the heading's containment list.

[0504] Similarly to the heading format description, one exception according to the preferred embodiment of the invention to the network object page body format is for network interfaces of perimeter elements. An interface to a perimeter element requires the description of its Network Address Translation (NAT) configuration, comprising the translation from one address set to another. Such NAT information is listed before any other relationship notation under the heading, “Network Address Translation.”

[0505] Relationship Notation

[0506] In the preferred embodiment of the invention, services within both the offering and the requiring lists are noted in ascending order by port with the lowest port used in the case of multi-port services. Within each service, relationships are listed in the order of network object containment, starting with the current network object, with the name of the containing network object following the service name. For each relationship, list the network objects with which the current network object is allowed to have such relationship.

[0507] Network Object Page Footers

[0508] In the preferred embodiment of the invention, the network object page footer contains hyperlinks to both of the network object indexes, and the outcomes page.

[0509] Generation of Outcome Page

[0510] In the preferred embodiment of the invention, every outcome in the policy domain is listed on the outcome page in alphabetical order. Listed beneath each outcome are associated outcome components, their dispositions and criticality, in alphabetical order of outcome component name. A set of hyperlinks to all index pages is provided at the top and bottom of the outcome page.

[0511] Although the invention is described herein with reference to a variety of preferred embodiments, one skilled in the art will readily appreciate that other applications may be substituted for those set forth herein without departing from the spirit and scope of the present invention. Accordingly, the invention should only be limited by the Claims included below.