Despite a number of high-profile take-downs last year malicious spam is till on the rise.
Google says that every time it kills the source of high volume spam, the decrease in unwanted traffic bounces back to previous levels within weeks, sometimes even days.
A post on the Google Enterprise Blog states: "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."
The report says that there is no shortage of botnets out there, and that as soon as one is taken down, the spammers simply buy or rent another to take its place.
Google said that its Postini service had blocked more than 100 million virus-bearing messages a day during a recent spike in spamming activity.