Six bots are responsible for 85% of all spam, according to an analysis by Marshal. The Srizbi botnet is the largest single source of spam - accounting for 39% of junk mail messages – followed by the Rustock botnet, responsible for 21% of the spam. Spam coming from the Mega-D botnet was temporarily stemmed after control servers were taken out in mid-February. The estimated 35,000 zombie clients associated with the Mega-D botnet were infected with the Ozdok Trojan. After 10 days of inactivity, spam from compromised hosts began flowing again earlier this week, after hackers re-established control. Read more..