http://dailytech.com/article.aspx?newsid=4592
The iPods contain the Troj/Bdoor-DIJ trojan, which allows an attacker to access and control your system remotely. Apple has traced the source of the trojan to a single infected Windows machine at one of their manufacturers, and claims that "less than 1%" of the iPods shipped after September 12, 2006, are carrying the trojan.