Last year’s takedown of the Grum botnet was one the most fascinating ones so far, as it triggered a quick response from the botherders who tried to derail law enforcement efforts by setting up new C&C servers, but failed.
A few days after, they tried and failed again. You would think that would be the end of it, but it’s apparently difficult to give up such a reliable source of income.
According to researchers from Trustwave Spider Labs, Grum’s botmasters are at it again. After having established five new C&C servers and sending an encrypted spam template to the remaining functioning bots, they started spewing out pharmaceutical spam leading to illegal pharmacy websites.
While the volume of spam Grum currently sends out is still nowhere near that of its heyday, the botnet’s slow comeback is nothing to sneeze at.
“It seems this botnet is deeply rooted, that you couldn’t take it down by its branch and fruit, but by its roots,” the researchers point out.