A pre-release version of Windows 7 has been infected with malware and is currently being distributed on peer-to-peer networks.
The tainted version of the new operating system includes malware that downloads further files from the internet. Trend Micro has named the threat TROJ_AGENT.NICE.
Last month criminals attacked Mac PCs using a similar tactic. They added malware to pirated versions of Apple's iWork '09 suite and Adobe's Photoshop CS4 software.