Prior art

To identify the most relevant prior art for US patent 6795918, I will examine the "Patent Citations" section from the provided patent text, which lists documents cited by the examiner.

Here are the prior art references cited in US Patent 6,795,918, along with their publication/filing dates, brief descriptions, and the claims they potentially anticipate under 35 U.S.C. § 102:

Most Relevant Prior Art for US 6,795,918:

1. US 5,802,320 A

   • Full Citation: US 5,802,320 A to Sun Microsystems, Inc.
   • Publication Date: 1998-09-01 (Priority Date: 1995-05-18)
   • Brief Description: This patent describes a system for packet filtering of data packets at a computer network interface. It involves extracting filter criteria from incoming packets and testing them against a set of filter rules to either accept or reject the packet.
   • Potentially Anticipates Claims:
     • Claim 1: The "method for filtering a plurality of data packets" by receiving, extracting information, providing to a decision block for authorization, and dropping/permitting packets, where the protocol information includes transport types. US '320's teaching of extracting filter criteria and testing against filter rules directly anticipates the core filtering method.
     • Claim 10: The "computer security apparatus" with communication interfaces and a packet analyzer that stores protocol, source port, and destination port information, and uses a lookup table for authorization. The apparatus elements for packet filtering are directly anticipated by US '320.
     • Claim 21: The bidirectional "computer security apparatus" that filters both public-to-private and private-to-public network traffic. The general concept of a packet filtering apparatus, as described in US '320, serves as a foundational reference.
     • Claim 25: The "service level computer security apparatus" described in means-plus-function format, as it directly mirrors the method of Claim 1, which is anticipated.
     • Claim 26: The "method for converting an unsecured digital transmission line into a secured digital transmission line" by inserting such an apparatus. If the apparatus itself is anticipated, the method of its deployment for securing a line is also anticipated in its general concept.

2. US 5,222,120 A

   • Full Citation: US 5,222,120 A to MCI Communications Corporation
   • Publication Date: 1993-06-22 (Priority Date: 1990-04-23)
   • Brief Description: This patent describes a long-distance telephone switching system with enhanced subscriber services. While not directly a computer network security patent, it relates to managing and routing communications based on service parameters.
   • Potentially Anticipates Claims: This patent's relevance to the specific packet filtering and service-level security of US 6,795,918 appears less direct compared to US '320. However, the general concept of controlling communication based on service information could be seen as broadly anticipating aspects of Claim 1, 10, 21, 25, and 26 related to service authorization, though not the specific technical implementation of packet filtering for computer networks.

3. US 6,026,379 A

   • Full Citation: US 6,026,379 A to Verifone, Inc.
   • Publication Date: 2000-02-15 (Priority Date: 1996-06-17)
   • Brief Description: This patent describes a system, method, and article of manufacture for managing transactions in a high availability system. It focuses on transaction management and system reliability, rather than specific network packet filtering for security.
   • Potentially Anticipates Claims: Similar to US '120, this patent's direct relevance to the packet filtering and service-level security aspects of US 6,795,918 is limited. Its focus on managing transactions might broadly touch upon the idea of permitting or dropping data based on certain criteria, but it does not appear to directly anticipate the specific technical features of US 6,795,918's claims in the context of computer network security.

4. US 4,709,136 A

   • Full Citation: US 4,709,136 A to Toppan Moore Company, Ltd.
   • Publication Date: 1987-11-24 (Priority Date: 1985-06-04)
   • Brief Description: This patent describes an IC card reader/writer apparatus. This technology is unrelated to computer network security or packet filtering.
   • Potentially Anticipates Claims: This patent does not appear to anticipate any claims of US 6,795,918 as it relates to a completely different field of technology.

Based on this review, US 5,802,320 A is the most relevant prior art for US 6,795,918, as it directly addresses the core concepts of packet filtering and authorization that are central to the claims of US 6,795,918.