Action taken by Microsoft and law enforcement agencies was responsible for the takedown of the infamous spam-spewing Rustock botnet, the software giant said today.
Anti-spam firms were taken by surprise by the abrupt cessation of junk mail from zombie clients in the Rustock botnet network on Wednesday afternoon. The reason for the respite, it emerged on Thursday, was a lawsuit by Microsoft that resulted in a series of coordinated raids targeting systems identified as being integral to the botnet's command and control network, as explained in a blog post by Microsoft here.
The raids involved the seizure of kit at seven US-based hosting facilities by US Marshals who teamed up with investigators in Microsoft's digital crimes unit to run the exercise, codenamed Operation b107. The operation followed similar tactics to the similarly organised takedown of the Waledac botnet last year, using a combination of legal and technical measures. The Rustock botnet takedown effort was a still more complex affair, Richard Boscovich, a senior attorney in Microsoft Digital Crimes Unit explains.
Microsoft filed suit against the anonymous operators of the Rustock botnet, based in part on the abuse of Microsoft trademarks in the bot's spam. However, Rustock's infrastructure was much more complicated than Waledac's, relying on hard-coded Internet Protocol addresses rather than domain names and peer-to-peer command and control servers to control the botnet.
To be confident that the bot could not be quickly shifted to new infrastructure, we sought and obtained a court order allowing us to work with the US Marshals Service to physically capture evidence onsite and, in some cases, take the affected servers from hosting providers for analysis.
As well as following up on the analysis work, Microsoft's most pressing priority on Rustock is to work in co-operation with national CERTs to organise the clean-up of the estimated one million zombie PCs that formed the Rustock botnet – and which remain infected.
Rustock, which specialised in sending junk mail adverts for sites that sell unlicensed pharmaceutical drugs, was responsible for sending an estimated 39 per cent of global spam in circulation last year, according to Symantec. ®