Witty worm

The Witty worm is a computer worm that attacked the firewall and other computer security products written by a particular company, Internet Security Systems (ISS) now IBM Internet Security Systems. It was the first worm to take advantage of vulnerabilities in the very pieces of software designed to enhance network security, and carried a destructive payload, unlike previous worms. It is so named because the phrase "(^.^) insert witty message here (^.^)" appears in the worm's payload.

The Witty worm incident was unique in that the worm spread very rapidly after announcement of the ISS vulnerability (a day later), and infected a much smaller and presumably harder-to-infect (because the administrators had taken security measures) host population than previous worms.