Just days after announcing that Dutch authorities took down two secondary servers used by the Grum botnet, FireEye late Wednesday reported that the entire botnet has been knocked offline, with all known command and control servers left without a heart beat—or at least without connectivity to the Internet.
With origins dating back to 2008, the Grum botnet, the world’s third largest botnet and one that is assumed to be responsible for approximately 17% of the World’s spam, has now followed the fate of several other large botnets that have been knocked offline.
After the takedown of secondary C&C servers earlier this week, FireEye, assisted by other industry experts and network operators around the world, were engaged in a game of cat-and-mouse with the cybercriminals behind the botnet to take down the primary C&C servers.
The botnet, which was built in two different segments, had one segment controlled by a server in Panama and the other from a server in Russia.
After successfully taking down the server in Panama, FireEye noticed that bot herders quickly started pointing the rest of the C&Cs to new secondary servers setup in Ukraine.
“The bot herders replaced the two Dutch servers with six new servers located in Ukraine. Ukraine has been a safe haven for bot herders in the past and shutting down any servers there has never been easy,” Atif Mushtaq, Senior Staff Scientist at FireEye explained in a blog post.
Quickly reacting to new details on the botnet's new infrastructure, Mushtaq and his team worked with fellow security industry experts including folks from Spamhaus and CERT-GIB, and hunted down contacts that were able to cut off the C&C servers from the Internet. Unlike a traditional takedown at an ISP or datacenter, Mushtaq said it was actually the upstream provider who null routed the server’s IP address at their request.
What results has FireEye and its partners been able to see as a result of the takedown? Data coming from Spamhaus shows that, on average, 120,000 Grum IP addresses were identified assending spam each day. But after today’s takedown, the number is down to 21,505. “I hope that once the spam templates expire, the rest of the spam with fade away as well,” Mushtaq said.
While keeping a botnet down for the count can sometimes be challenging, FireEye’s Mushtaq believes the future of the botnet fights is looking brighter. “There are no longer any safe havens,” he said. “Most of the spam botnets that used to keep their C&Cs in the USA and Europe have moved to countries like Panama, Russia, and Ukraine thinking that no one can touch them in these comfort zones. We have proven them wrong this time.”
“When the appropriate channels are used, even ISPs within Russia and Ukraine can be pressured to end their cooperation with bot herders,” Mushtaq concluded.
So, will the spammy Grum botnet remain offline and down for the count? Or will it resurface like several other botnets have? It’s hard to tell, but FireEye says the botnet doesn’t have any apparent fall back mechanisms that would allow it spin back up easily in the days to come. That being said, sometimes the only way to permantely keep a well-built botnet offline for good is to hunt down the cybercriminals behind it.
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