Abstract: A network system by the present invention can quickly detect viruses and does not easily become a new cause of vulnerability. A packet data comparator branches inputted packet data into three branches, and includes an additional pattern matching unit which compares the branched data with the stored data and performs matching with collation patterns stored in a rewritable storage area, a fixed pattern matching unit which compares the branched data with the stored data and performs the matching with a logical operation configured with known collation patterns, a notification packet matching unit which compares the branched data with the stored data and finds a notification packet, and an identity detection aggregation unit which aggregates results from the respective matching units. Moreover, a virus filter, a virus checker, and a secure network system are realized by using the present invention.

Abstract: It is an object of the present invention to realize a network system which can quickly detect a virus and tends not to be a new cause of vulnerability. A packet data comparator disclosed by the present invention branches inputted packet data into three branches, and includes an additional pattern matching unit which compares the branched packet data with a part of stored data and performs matching with collation patterns stored in a rewritable storage area, a fixed pattern matching unit which compares the branched packet data with the part of the stored data and performs the matching with a logical operation which has been configured with known collation patterns, a notification packet matching unit which compares the branched packet data with the part of the stored data and finds a notification packet, and an identity detection aggregation unit which aggregates results from the respective matching units.