Storm, the Trojan that hoovers PCs into hacker-controlled botnets, <A HREF="http://www.infoworld.com/article/07/08/14/Record-breaking-Storm-Trojan_1.html">roared back into life last month</A> in several waves, security researchers said Monday, and has blown by 2005's Sober to become the most prolific email-borne malware ever.

"This is the biggest since Sober in mid-to-late 2005," said Sam Masiello, the director of threat research at MX Logic, referring to a long-lasting worm whose variants struck repeatedly in the second half of 2005, often in extremely high numbers. In November 2006, for instance, email filtering companies reported malware-laden email counts spiking 1,500 percent in a week, and said they were intercepting four times the usual number of infected messages.

According to MX Logic, Storm--a bot Trojan that collects compromised computers into large networks of ready-to-use PCs--has broken Sober's records. Thanks to Storm, the Englewood, Colo. managed email security vendor tracked a July jump in malicious email of 1,700 percent over June.