11. The system of claim 9 wherein the portions of the data stream stored in the buffer include a portion available for scanning and a portion that has already been scanned.
9. A system for scanning computer network traffic for viruses, the system comprising: a buffer configured to store portions of a data stream; a plurality of script patterns, each script pattern in the plurality of script patterns comprising a set of instructions for identifying a particular network virus, each script pattern in the plurality of script patterns being created using a scripting language that allows for conditional flow control to allow conditional branching to a line of a script pattern; and a script engine configured to execute the script patterns to check the data stream for network viruses.