As you have probably already heard, the Grum botnet – formerly the third largest in the world – has been effectively shut down last week after several security researchers managed to coordinate the takedown of its last-standing C&C servers in Ukraine and Russia.
Expectedly, the botnet’s herders have not sat idly by while their livelihood was threatened, and they mounted a last-ditch attempt at regaining control of at least one segment of the botnet.
“In the absence of any built-in fallback mechanisms, the bot herders used another fallback mechanism that is called money,” FireEye’s Atif Mushtaq reported yesterday.
“Over the weekend we found that the Ukrainian ISP SteepHost removed the null route on three CnCs that were taken down last week. We suspect the bot herders must have paid a large amount of money in order to get access to these servers.”
The move resulted in a short burst of spam sent by the botnet, but any further action was quickly thwarted by security researchers who contacted SteepHost and negotiated once more the shutdown of the servers in question.
The ISP says that the servers were back online due to break-ins and security related issues. Still, they were effectively threatened with the possibility of getting de-peered off the Internet by their upstream provider or of getting their subnet blacklisted if something like this happens again.