Friday Open Thread > Watch out - P2P MP3s are being infected with malware

A new kind of malicious software could pose a danger to Windows users who download music files on peer-to-peer networks.

The new malware inserts links to dangerous Web pages within ASF (Advanced Systems Format) media files.

If a user plays an infected music file, it will launch Internet Explorer and load a malicious Web page which asks the user to download a codec, a well-known trick to get someone to download malware.

The actual download is not a codec but a Trojan horse, which installs a proxy program on the PC, Emm said. The proxy program allows hackers to route other traffic through the compromised PC, helping the hacker essentially cover their tracks for other malicious activity, Emm said.

The ".mp3" extension of the files is not modified, however, so victims may not immediately notice the change, according to Kaspersky Lab.

Most savvy PC users are aware of the codec ruse, but the style of attack is still effective since many media players do need to receive updated codecs occasionally in order to play files.

"Users downloading from P2P networks need to exercise caution anyway, but should also be sensitive to pop-ups appearing upon playing a downloaded video or audio stream," Secure Computing said.

"I think that outside a minority of users who really know about all the dangers implied with Internet use, the vast majority of people have no idea that such a codec download could lead to a Trojan infection," Citay wrote.

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