1. In anti-virus and intrusion detection systems, a signature is a pattern that the system will look for when scanning files or network traffic. (Note: this term is unrelated to digital signatures). Key point: Marketing forces often mean that companies have to fill their products with useless signatures. Don't be impressed because one product has more signatures than another. Key point: One of the key goals of hacking is to evade signature detection. Virus writers attempt to encrypt their viruses, whereas remote hackers attempt to alter the networking protocol so that it has the same effect, but a different pattern on the wire. From Hacking-Lexicon