A major spam botnet that inundated email inboxes around the world with emails promoting fake prescription drugs is gone. So says the security firm that helped kill it. “The Grum botnet has finally been knocked down. All the known command and control (CnC) servers are dead, leaving their zombies orphaned,” wrote Atif Mushtaq of FireEye Malware Intelligence Lab in California, referring to computers enslaved by hackers for malicious use. The security firm worked with The Spamhaus Project, computer experts and Internet service providers around the world in the effort. The botnet has been around for about four years, and “has lately been responsible for about 15 to 17 percent of all spam,” Vincent Hanna of The Spamhaus Project, told NBC News Thursday. Read the full story at NBC News.