said by Jason Levine
:How do you get a trojan in an MP3 file? I can understand if the file is names SomeSong.mp3.exe and the user has extensions hidden. Then they just see "SomeSong.mp3" but the file itself is an executable. However, when Windows sees a file with a .mp3 extension, it opens a program that has been assigned to open MP3 files (Windows Media Player, WinAMP, QMP, etc). If that player has some sort of bug that allows the MP3 file to run executable content, that's one thing. But an MP3 file that actually contains a trojan? Something doesn't seem right about that.
It looks like the .mp3 file is redirecting users after they run it to download another file called PLAY_MP3.exe and that is what infects the users.