Abstract: Detection of a signature in a data packet comprises performing a pre-classification of the packet, using header information and particularly a 5-tuple access control list, into one of a multiplicity of flows and directing the payload of the packet to a respective one of a multiplicity of deterministic finite state machines each of which stores a plurality of signatres as a sequence of states and acts only on the respective flow.

Abstract: A search engine operable to search on a search key word of a given length comprises a trie database which supports a trie search on keys of the given length and a content addressable memory organized to receive a most significant section of the search key word. The search engine performs a full trie search on the whole of said search key word in the event of no match of a most significant section within the content addressable memory. In the event of a match within the content addressable memory the search engine performs a partial trie search commencing with a trie block pertaining to a first segment of the search key word after the most significant section which has already been matched.