A reward of $250,000 (£172,000) has been offered by Microsoft to find who is behind the Downadup/Conficker virus.

Since it started circulating in October 2008 the Conficker worm has managed to infect millions of Windows computers.

The software giant is offering the cash reward because it views the Conficker worm as a criminal attack.

“People who write this malware have to be held accountable,” said George Stathakopulos, of Microsoft’s Trustworthy Computing Group.

Read more about the Confiicker Worm.