The Grum botnet was the third-most prolific botnet in the world, with a third of all spam worldwide. Botnet hunters were able to pull the plug on servers in Russia and the Ukraine, a region favored by cybercriminals. FireEye says this should scare other botnet groups a bit, demonstrating that this region isn’t such a safe haven after all. The botnet most recently had some 100,000 active bots, according to FireEye, which says it has seen a drop in spamming from Lethic.”]
Source: https://www.darkreading.com/attacks-breaches/final-blow-kills-remainder-of-grum-botnet