February 16, 2009

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. He told BBC News the company was "not prepared to sit back and let this kind of activity go unchecked".

"Our message is very clear - whoever wrote this caused significant pain to our customers and we are sending a message that we will do everything we can to help with your arrest," said Mr Stathakopulos.

Arbor Networks said as many as 12 million computers could be affected globally by Conficker/Downadup since it began prowling the web looking for vulnerable machines to infect in October

The Conficker worm is a self-replicating program that takes advantage of networks or computers that have not kept up to date with Windows security patches. It can infect machines via a net connection or by hiding on USB memory drives used to ferry data from one computer to another. Once in a computer it digs deep, setting up defences that make it hard to extract.

The worm slithers through networks by guessing usernames and passwords. Security specialists recommend hardening passwords by mixing in numbers, punctuation marks and capital letters. The virus reports in to its creators for updates by visiting a web domain. It generates the name of the domain itself using a complicated code which security firms have cracked to track the growth of the worm and block its progress.