Fakepatch is a worm that propagates by e-mail through messages with infected attachments. Once the user executes such an attachment, the parasite secretly installs itself to the system and runs a spreading routine. Fakepatch gathers user contacts from the Yahoo! Messenger program and uses them to send out malicious e-mails, which purportedly offer an important patch for Yahoo! Messenger. The worm does not carry any destructive payload. Fakepatch runs on every Windows startup.