15. A method of scanning computer network traffic for viruses, the method comprising: parsing a protocol of network data packets received over a network; extracting payloads of the network data packets; storing the payloads as data stream in a buffer; scanning portions of the data stream in the buffer for network viruses using a plurality of script patterns, each script pattern in the plurality of script patterns comprising a set of instructions for identifying a network virus, at least a first script pattern in the plurality of script patterns including an instruction for allowing conditional branching to a line of the first script pattern.
18. The method of claim 15 wherein the first script pattern includes an instruction for storing and retrieving data from a stack.