Annunci is an Internet worm that propagates by e-mail through messages with infected attachments. Once the user opens such an attachment, the parasite secretly installs itself to the system and runs a spreading routine. It sends bogus letters to addresses it gathers from the Microsoft Outlook mail program. Then it runs a payload. Annunci connects the compromised computer to the Internet by dialing a high-cost phone number using a modem. It also blocks access to MSN Search, changes the Internet Explorer default home page and creates several shortcuts leading to infected files. The worm automatically runs on every Windows startup.