California-based security firm FireEye and U.K.-based spam-tracking service SpamHaus traced the spam back to servers in Russia and "worked with local ISPs to shut down the servers, which ran networks of infected machines called botnets," CNET writes
FireEye worked with other experts in the worldwide security industry to apply pressure to local ISPs to suspend the illegal operation, according to BBC News
"When the appropriate channels are used, even ISPs within Russia and Ukraine can be pressured to end their cooperation with bot herders," said
Atif Mushtaq, a security researcher with FireEye. "There are no longer any safe havens. Most of the spam botnets that used to keep their CnCs 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."
At its peak, Grum was known as the the world's most prolific spam machine, "though researchers recently dropped it to the number three spot on their ever-changing list of the world's largest botnets," CNNMoney writes
Grum was a fan of spreading fake prescription drugs emails, and before the takedown, Grum spam messages originated from 100,000 to 120,000 IPs every day and approximately 500,000 every week, according to PC World
Earlier this year, Microsoft, Facebook, Google and Yahoo formed
the technical working group, Domain-based Message Authentication, Reporting and Conformance (DMARC) to fight email spam. The group claims it can stop attacks through policy-based steps to filter out spam.