CWmike writes: "Microsoft said Tuesday that the coordinated take-down of the Rustock botnet and follow-up efforts had purged the malware from over half of the PCs once controlled by Russian hackers. 'This shows that disruptive action [against botnets] is viable and possible,' said Richard Boscovich, a senior attorney with Microsoft's Digital Crime Unit. 'Once you start taking apart the infrastructure of botnets, you drive up the cost of [botnet gangs] doing business," Boscovich told Computerworld. 'Disruptive action is just as good as trying to arrest someone.' Since March, when Microsoft lawyers and U.S. Marshals seized Rustock command-and-control servers at five Web hosting providers in seven U.S. cities, the number of Windows PCs infected with the malware has dropped worldwide from 1.6 million to just over 700,000 as of June 18, Boscovich reported in a blog post Tuesday. Microsoft also released a detailed report (PDF document) on Rustock, the take-down effort it led, and the impact of its anti-botnet campaign."