A new botnet is on the scene, and it's overtaken the Storm worm's. Called Mega-D, it is currently responsible for 32% of all spam mails sent, 11% more than the Storm Worm botnet at its peak last September. Mega-D's botnet heavily promotes so called "male enhancement" pills and several other pharmaceutical products. It uses news headlines, including the recent death of actor heath ledger, to trick recipients into opening the message, and comes with a Trojan designed to add the recipient's computer to the botnet.

"[Mega-D] probably started about four months ago and it's been steadily increasing since then," said Bradley Anstis, vice-president of products at Marshal, a security vendor."It is possible that the individuals behind the Storm botnet are responsible for one or more of these other botnets."

Marshal now estimates the Storm worm's botnet is now responsible for just 2% of the world's spam.