Microsoft announced Monday that it is issuing a monetary reward in the amount of US$250,000 for new information that results in the arrest of operators of the Rustock botnet.

"In order to determine the identities of the John Doe defendants principally responsible for the control of the Rustock botnet, Microsoft Corporation is offering a $250,000 reward for any new information that results in the identification, arrest and criminal conviction of whoever is responsible," the operating systems giant said in a notice.

In March, Microsoft and other software vendors teamed up with federal law enforcement agents to seize computer equipment from US Internet hosting facilities to cripple the network that was blamed for sending 30 billion spam mails everyday.

After publishing notices in two Russian newspapers last month to notify the Rustock operators of the civil lawsuit. Microsoft is offering a reward stemming from its recognition that the Rustock botnet is responsible for a number of criminal activities and serves to underscore our commitment to tracking down those behind it.

"While the primary goal for our legal and technical operation has been to stop and disrupt the threat that Rustock has posed for everyone affected by it, we also believe the Rustock bot-herders should be held accountable for their actions," Richard Boscovich Senior Attorney, Microsoft Digital Crimes Unit, said in a blog post.

Besides accounting for a sizable portion of the world's spam, Rustock was responsible for a number of other crimes as well, including advertising counterfeit or unapproved versions of pharmaceuticals, and violating the trademarks of the pharmaceutical manufacturer Pfizer and Microsoft, Boscovich said.

"Additionally, although the Rustock botnet infection base has been cut in half in the short time since the takedown, there are still hundreds of thousands of infected computers around the world yet to be cleaned of the botnet malware" he added.

Although the botnet has remained inactive since March, its operators are still at large and there are still hundreds of thousands of computers infected by Rustock.

Microsoft said residents of any country are eligible for the reward pursuant to the laws of that country, because the Rustock botnet affected the Internet community worldwide. If you have any information to share, you can contact Microsoft via avreward@microsoft.com.