Krebs on Security is reporting that a huge drop in the volume of e-mail spam circulating worldwide on Wednesday was the result of a planned takedown of the Rustock botnet
, which, at one point, was the most prolific purveyor of spam in the entire world. According to the Composite Spam Blocklist (CBL), which measures global spam volumes, Rustock spam (usually ads for online pharmacies and male enhancement pills) vanished at around 10:45 EST on Wednesday. Another Rustock watchdog, SecureWorks director of malware research Joe Stewart, told Krebs that none of the 26 Rustock networks he'd been watching were responding on Wednesday afternoon either. "It looks to me like someone has gone and methodically tracked these [addresses] and had them taken out one way or the other," Stewart said. It isn't clear, however, exactly who is behind this takedown, if that's the case.
This isn't the first time it's Rustock has gone quiet
. The problem is that Rustock has infected about 815,000 PCs around the world, according to an estimate from the CBL. As long as these machines are active, the zombie network can be reanimated through a preexisting algorithm that tells the bots to visit a website that contains software updates and new instructions for spreading spam. That's why we'd put our money on this drop-off being temporary rather than permanent. But it doesn't mean we can't (and won't) enjoy our less congested inbox for the few days or weeks that Rustock remains offline.