Patent ID: 7957390

Claim:
A method of detecting digital signatures in messages transmitted over a packet based network, said messages being composed of message segments having a predefined order, said method comprising: processing a first received message segment using a deterministic finite state automaton (DFA) operating on a network unit, said DFA defining each of a plurality of digital signatures associated with unwanted intrusion as a respective succession of states; storing a first state of the DFA after processing the first received message segment and forwarding the first received message segment; receiving a third message segment out of the predefined order; processing the third message segment using the DFA starting at a null state; receiving a second message segment following processing of the third message segment, wherein the second message segment is a next message segment in the predefined order following the first received message, wherein the third message segment is a next message segment in the predefined order following the second received message; and processing the second message segment using the DFA starting at the stored first state.