Microsoft (Nasdaq: MSFT) has offered a US$250,000 worldwide reward for new information on the operators of botnet Rustock, the company said in a statement.
The Russian botnet network had been sending spam to users all over the world, including countries like Brazil, until it was shut down earlier this year.
"Microsoft Corporation is offering a US$250,000 reward for any new information that results in the identification, arrest and criminal conviction of whoever is responsible for the control of the Rustock botnet," the statement said.
Richard Boscovich, senior attorney of Microsoft's digital crimes unit, said in his blog that after publishing notices in two Russian newspapers last month to notify Rustock's operators of a civil lawsuit, the company has decided to increase efforts to identify those controlling the botnet by issuing a monetary reward.
"We believe the Rustock bot-herders should be held accountable for their actions," Boscovich said.
Rustock was able to send some 30bn spam messages a day, including advertising counterfeit or unapproved versions of pharmaceuticals, and violating the trademarks of the pharmaceutical manufacturer Pfizer and Microsoft.