Somebody “almost” succeed to create a virus for iPod and I say “almost” because it is really difficult to make it run, (even if you want to infect your iPod).
The virus name is Oslo
They call it a proof of concept, so this virus have been developed just to show that an iPod running Linux can be infected with a virus.
Anyway there is almost nothing to worry about, according with: http://www.viruslist.com/weblog (April 5th post) there is nothing to worry about, read what they say.
“Overall, I don’t think iViruses will cause serious problems in the future. The iPod world is very different from the PC and smartphone world. Users aren’t constantly installing new software and downloading a wide range of files, so that cuts down on the possible infection vectors. And what’s there to steal from an iPod? Multimedia files, and that’s about all.”