Spam volumes have plummeted following the demise of a Web hosting firm that was allegedly helping some of the world's worst junk e-mail gangs.

Last week there was a coup when spam fighters took down McColo, a U.S.-based company apparently catering to bulk e-mailers. Apparently, spam levels fell over night. Worldwide spam volume was about 153 billion e-mail messages on Nov. 11, the day McColo's Internet providers yanked its service. In two days, that dropped to 64 billion messages, according to IronPort, a security firm owned by Cisco Systems Inc.

Things have started to pick up again with other suppliers moving to fill the gap. Security firm Sophos reported Sunday that McColo was back online again after scoring service from a Swedish Internet provider. The service was withdrawn after the Internet provider heard from security researchers.

IronPort said that spam volume was climbing, and had reached an estimated 71 billion messages.