The close of webhosting firm McColo gave spammers a big blow in late 2008, with spam levels dropping by 70 percent according to anti-spam firm Ironport. It took spammers a couple of months to recover, and unfortunately spam levels are once again soaring. NY Times reports spam now accounts for 94 percent of all e-mail, roughly the same level as before the shutdown of McColo.
Even worse is that spammers are now building more decentralized botnets, which can't be shut down as easily as McColo:
But this year, average spam volumes have increased about 1.2 percent each day. And there is evidence that spammers are now building more decentralized, peer-to-peer spamming botnets that no longer rely on the visible and vulnerable control nodes that they were using at McColo to guide their spam e-mail campaigns.
“What the spammers have been using to rebuild is more technically advanced than what got taken out and is itself a more resilient technology,” Mr. Swidler said. “It’s unlikely we are going to see another event like McColo where taking out an I.S.P. has that kind of dramatic impact on global spam volumes.”