A federal magistrate judge has recommended that Microsoft be given ownership of 276 internet addresses used to control “Waledac,” a massive botnet that the software company has been working to bring down.

The recommendation by Magistrate Judge John F. Anderson of the US District Court for Eastern Virginia is a victory in Microsoft's experimental campaign to wrest control of one of the net's biggest menaces. The effort, which commenced in February, has combined technical and legal maneuvers in an attempt to disrupt Waledac, which was once one of the 10 biggest botnets and a major distributor of spam.

Just a few weeks after the launch of Operation b49, as Microsoft dubs the takedown, as many as 90,000 zombie PCs lost contact with the command and control channels used to send malware updates that keep them infected. It was the result of a novel move, in which Microsoft lawyers sought a temporary order that seized control of 277 domain names used to administer the channels.

“To date, we have seen virtually no reemergence of Waledac traffic,” Jeff Williams, principal group program manager for Microsoft's Malware Protection Center, wrote on Wednesday. “This puts the Waledac takedown among a very few successful efforts to shut down a botnet without having it re-emerge.”

The failure of Waledac to rise from the grave is in stark contrast to other takedown efforts. In March, for instance, a series of Zeus botnets was resurrected less than 48 hours after security white hats tried to take it down.

Of the 277 domain names Microsoft pursued, only one was claimed, and that was by an Oregon man who ran a website that had been compromised, Williams said. The remaining owners still have a week or so to come forward, but that doesn't seem likely. If adopted, Anderson's recommendation would make February's temporary order permanent. Microsoft has more about the development here.

Operation b49 has another component that is equally novel. Armed with data captured from the command and control servers, Microsoft has detailed information about the hundreds of thousands of PCs that were infected by Waledac. The company is now reaching out to the ISPs of those head-spinning, demonized machines so they can seek a proper exorcism.

Cox Communications, a US-based provider that has long quarantined infected subscribers in rubber rooms, has already contacted several hundred customers to guide them to free tools from Microsoft that will disinfect the machines.

Operation b49 is the first initiative of a larger project known as MARS, or Microsoft Active Response for Security. Williams said there's more to come. ®