The Mobile Antivirus Researchers Association claims to have detected the first worm that can jump from a PC to a Windows Mobile-powered wireless device. 

The 'Crossover' worm nests itself in a directory on a Windows PC where it will automatically activate once the user connects a Windows Mobile device using Microsoft ActiveSync.

The digital pest was sent to the association anonymously and is a proof-of-concept designed to show off its features but not cause any actual harm.

"This is proof-of-concept code for educational purposes only. This virus closes the gap between handhelds and desktops. Now it's one big world open to all," the worm creators said in a note attached to the virus.

Antivirus vendors have been warning for years about the threat of viruses targeting mobile devices. 

McAfee said last week that it has detected over 200 mobile viruses and warned that mobile pests are outgrowing those targeting PCs.

Worms for Windows Mobile are still relatively rare, however. The first virus for Microsoft's mobile operating system dates back to July 2004, and a search on Symantec's Security Response website turned up only a handful of viruses for the platform.