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.”