Vundo is a widely-spread trojan that displays large amount of unsolicited pop-up advertisements. The parasite also silently downloads from the Internet and runs arbitrary potentially harmful files, mostly adware components. Vundo is distributed by e-mail in messages containing links to insecure web sites, which exploit certain security vulnerabilities of the Internet Explorer web browser. Once the user clicks on such a link, Internet Explorer opens a dangerous site that automatically installs the trojan into the system without user knowledge and consent. Vundo is responsible for the severe decrease of the amount of system virtual memory available. This results in noticeable computer performance slowdowns. Vundo secretly runs on every Windows startup.