Anti-virus firm Sophos said there was confusion about exactly which virus was onboard the iPods.

"There are a number of different pieces of malware which use a file called RavMonE.exe," said Graham Cluley, senior technology consultant for Sophos, "so we don't know at the moment precisely which trojan horse or virus may have been shipped."

The virus in question could be part of the RJump virus family which tries to steal information and open a back door into an infected PC.