Security Experts:

Dutch Police Takedown C&Cs Used by Grum Botnet

Researchers at malware intelligence firm FireEye are reporting that Dutch authorities have pulled the plug on two secondary servers used by the Grum botnet. The removal of the servers shines light on how quickly some law enforcement agencies work, given that proof of their existence is just over a week old.

Grum BotnetLast week, FireEye published the details on four servers, actively controlling the Grum botnet. These servers, two in the Netherlands, one in Panama, and one in Russia, were split into primary and secondary roles. The backup C&Cs were located in the Netherlands, and once word of their existence was released, Dutch authorities quickly seized them.

“The intention behind this article was not only to share this information for a general awareness, but I hoped that the research community would come forward to take down this spam beast. I can see that this strategy is really working. Dutch authorities have pulled the plug on two of the CnC servers...,” wrote FireEye’s Atif Mushtaq in a follow-up blog post.

Grum is the world’s third largest botnet, producing some 17% of the total spam that floods email boxes daily. While the takedown of the secondary servers is expected to have some impact on the spam volume, it is understood that the impact will be minimal.

This is because the two primary servers are fully active, and the datacenters hosting them are unresponsive to fully documented abuse reports. “This means that using these two live servers, the bot herders might try to recover their botnets by executing a worldwide update. No action has been taken by the bot herders so far. There is complete silence from their side.”

That being said, Mushtaq noted that the botnet does has some weak spots, including the fact that Grum has no failback mechanism, has just a few IPs hardcoded into the binaries, and the botnet is divided into small segments, so even if some C&Cs are not taken down, part of botnet can still remain offline.

Progress on the War on Spam

While it may be hard to believe, Mushtaq think that a Spam free inbox may not just be a pipe dream and is just a few takedowns away. "In my opinion, taking down the top three spam botnets—Lethic, Cutwail, and Grum—is enough for a rapid and permanent decline in worldwide spam level," he said. "We still have to deal with small players, but I am sure that, after seeing the big players being knocked down, they will retreat as well."

FireEye has been monitoring and exploring the world’s largest botnets. Details on Grum appeared in part five of their series. The first, appearing in 2009, can be seen here

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Steve Ragan is a security reporter and contributor for SecurityWeek. Prior to joining the journalism world in 2005, he spent 15 years as a freelance IT contractor focused on endpoint security and security training.