Koobface

Koobface is a multi-platform computer worm that originally targeted users of the social networking websites Facebook email (its name is an anagram of "Facebook"), MySpace, hi5, Bebo, Friendster and Twitter. In the later versions it has stopped using those social networks so extensively because they improved their protection. Koobface is designed to infect Microsoft Windows and Mac OS X, but also works on Linux (in a limited fashion).