W32.Swen.A@mm is a mass-mailing worm that uses its own SMTP engine to spread itself. It attempts to spread through file-sharing networks, such as KaZaA and IRC, and attempts to kill antivirus and personal firewall programs running on a computer. The worm can arrive as an email attachment. The subject, body, and From: address of the email may vary. Some examples claim to be patches for Microsoft Internet Explorer, or delivery failure notices from qmail. Read More W32.Swen.A@mm is similar to W32.Gibe.B@mm in function, and is written in C++. This worm exploits a vulnerability in Microsoft Outlook and Outlook Express in an attempt to execute itself when you open or even preview the message. Information and a patch for the vulnerability can be found at http://www.microsoft.com/technet/security/bulletin/MS01-020.asp Get more informations about Swen over here