A new malware uses MP3’s to infect the computers of peer-to-peer users, by inserting links to insecure web sites, on ASF media files. As David Emm, senior technology consultant for security vendor of Kaspersky Labs said, this was the first time they’ve seen it done, even though they knew of this possibility for some time now.

When you try to play the infected MP3, the Internet Explorer opens in a dangerous web site, asking you to download a codec needed to play the file. The truth is that you download a Trojan horse, which installs a proxy program on your computer to help the “hackers to route other traffic through the compromised PC, helping the hacker essentially cover their tracks for other malicious activity”,

Most people think that downloading a codec to play the file, is a natural procedure of their player. The best, and of course most secure, thing to do is to decide by yourself which codec you’ll download.

Kaspersky calls the malware "Worm.Win32.GetCodec.a", Trend Micro calls it "Troj_Medpinch.a” and “Secure Computing names it "Trojan.ASF.Hijacker.gen".