The role botnets play in the spam volume isn't exactly new, either, but is particularly troubling because of the early June much-touted FTC takedown of Pricewert, an ISP that carried a lot of botnet Cutwail's spam freight.
The fact that Cutwail had regained as much as a third of its spam-generating volume within hours of the Pricewert shutdown indicates that the spammers are getting better at self-preservation, with redundancies and backup plans that make a large interuption of sdpam from the takedown of a single source, such as last fall's McColo shutdown, increasingly unlikely.
Because botnets can hit small and midsized businesses hard, and because the botnet operators are getting so good at keeping their creations up and running, it's more important than ever that you, and all of your employees maintain the highest levels of defense against them, and do so constantly.
The botnets aren't taking a break, and neither can you.
The complete MessageLabs June 2009 Intelligence Report is available here.