In 2009, the security community started seeing diminishing returns from the takedown of malicious ISPs. After the ISP 3FN was taken down, spam levels rebounded in less than a month, and after Real Host went down, spam volumes recovered after only two days. In response, the anti-spam community turned its attention toward taking botnets offline instead.


Toward the end of 2009, Mega-D, a top-10 botnet – responsible for infecting more than 250,000 computers worldwide – was severely crippled through a carefully orchestrated campaign designed to isolate the command-and-control servers spammers were using to support the botnet. In early 2010, security professionals, along with government agencies, successfully mounted a campaign against several more targets: major botnets such as Waledac, Mariposa, and Zeus were either shut down or had their operations significantly curtailed.


However, this recent spate of botnet takedowns has not had a dramatic impact on spam levels. Although spam and virus levels did fall below Q4’09 highs, reports from Google’s global analytics show that spam levels held relatively steady over the course of Q1’10.