From today's NYT

There have been some recent successes, but they are short-lived. On Nov. 11, the volume of spam, which transports the malware, dropped by half around the globe after an Internet service provider disconnected the McColo Corporation, an American firm with Russian ties, from the Internet. But the respite is not expected to last long as cybercriminals regain control of their spam-generating computers.

“Modern worms are stealthier and they are professionally written,” said Bruce Schneier, chief security technology officer for British Telecom. “The criminals have gone upmarket, and they’re organized and international because there is real money to be made.”