This information was just passed to me by a friend, a few minutes ago, so I thought it important enough to pass along here.
McAfee is reporting a large uptick in the number of Trojan adware installs via bogus MP3 files on file sharing networks. Masquerading as audio files with real-sounding names, the Trojans install adware on users' PCs. Once someone tries to open the files, they are asked to sign an end-user agreement and then the program installs two Trojan files - NetNucleus and Mirar. Once installed, the infected machines start serving up popup ads. Over the last 24 hours, McAfee reports that nearly one third of all McAfee clients reporting results back to the company have detected these files.