Yautoit is an Internet worm that spreads through instant messages using the Yahoo! Instant Messenger program. Once executed, the parasite secretly installs itself to the system and starts a spreading routine. It sends bogus messages containing links to malicious web pages to other Yahoo! Instant Messenger users. Then Yautoit runs a payload. The worm changes the Internet Explorer default home page, disables the Task Manager and the Registry Editor, modifies some Yahoo! Instant Messager settings. The parasite also changes titles of Internet Explorer windows and locks the home page. Yautoit runs on every Windows startup.