Microsoft may have incapacitated the notorious Rustock botnet this year, but the company is still hunting those who were running the show. In March, Redmond paired up with federal law enforcement agents to seize computer equipment from US Internet hosting facilities to cripple the million-machine-strong network. Besides accounting for a sizable portion of the world's spam, Rustock committed other crimes, including advertising counterfeit or unapproved versions of pharmaceuticals, and violating the trademarks of Pfizer and Microsoft.

Only two weeks after being taken offline, global spam rates declined some 33.6% according to a Symantec MessageLabs Intelligence report. There are still hundreds of thousands of computers infected by Rustock, the total infection base has shrunk by half. Although the botnet has remained inactive since March 16, the former operators remain at large and Microsoft is committed to tracking them down. In a blog post today, the company announced a new initiative to augment the company's civil discovery efforts: money -- and lots of it.

Hoping to hasten the arrest of those responsible for Rustock, Redmond has put out a bounty (PDF) worth a quarter of a million dollars. "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 company said. If you have any information to share, you can contact Microsoft via avreward@microsoft.com.