Abstract: An electronic message filtering system and method is described. A message is received as input to the filter and decomposed into a set of components. The set of components is then processed through a pattern matching algorithm to determine if the message contents contains patterns inherent in a specified pattern, such as a natural language. The results of the pattern match analysis are output by the filter.

Abstract: A system and method for filtering electronic mail messages is described. A message is received an processed through a one or more filter flows. Each filter flow is comprised of one or more self-contained nodes which can be combined in whatever order is required to enforce a given security policy. Node independence provides a policy-neutral environment for constructing filter flows. A filter flow may be as simple as forwarding the mail to the intended recipient, or may perform one or more checks where it decides whether to forward, reject, return (or some combination thereof) the message. Certain node types are also able to append information on to a mail message, while others are able to modify certain parts of a mail message. Several of the node types are able to generate audit or log messages in concert with processing a mail message.

Abstract: A system and method for regulating the flow of messages through a firewall having a network protocol stack, wherein the network protocol stack includes an Internet Protocol (IP) layer, the method comprising establishing a security policy, determining, at the IP layer, if a message is encrypted, if the message is not encrypted, passing the unencrypted message up the network protocol stack to an application level proxy, and if the message is encrypted, decrypting the message and passing the decrypted message up the network protocol stack to the application level proxy, wherein decrypting the message includes executing a process at the IP layer to decrypt the message.

Abstract: A system and method for regulating the flow of internetwork connections through a firewall having a network protocol stack which includes an Internet Protocol (IP) layer. A determination is made of the parameters characteristic of a connection request, including a netelement parameter characteristic of where the connection request came from. A query is generated and a determination is made whether there is a rule corresponding to that query. If there is a rule corresponding to the query, a determination is made whether authentication is required by the rule. If authentication is required by the rule, an authentication protocol is activated and the connection is activated if the authentication protocol is completed successfully.

Abstract: A proxy which is part of a firewall program controls exchanges of messages between two application entities. The proxy interrogates attempts to send a communication session by requesting entities with a server entity in accordance with defined authentication procedures. The Proxy interfaces with networking software to direct a communication stack to monitor connection messages to any address on specific ports. The requestor's address, and the server's address are extracted from the messages and checked fo compliance with a security policy such as one including an access control list. If either address is invalid, the proxy deletes the message. If both are valid, the message is relayed, and the ports used are tracked for a predetermined time. Reply messages are then sent using the address of the server entity so that the proxy is transparent to the requester.