Botnet networks of compromised PCs are responsible for 87 per cent of all spam, according to figures released by Microsoft at the RSA Conference on Wednesday.
Adrienne Hall, general manager of Microsoft's Trustworthy Computing program, told delegates: "Botnets are the prime suspect in cybercrime, the core of the threat."
Hall unveiled a report that revealed that the Lethic zombie army was responsible for 56.7 per cent of botnet-sourced junk mail between March and June of 2010. Lethic agents are running on only 8.3 per cent of known botnet IP addresses, so each compromised machine is made to work extremely hard in churning out junk. "A takedown of the Lethic command and control servers in January 2010 disrupted the ability of spammers to distribute junk mail. However the Cybercrooks behind Lethic regained and re-established control of the botnet," the report said.
Microsoft reports that the Rustock and Cutwail botnets were the next two most prolific junk mail sources in Q2 2010, churning out 16.9 per cent and 15.4 per cent of botnet-manufactured spam respectively.
Redmond's statistics come from enterprise users of its Forefront Online Protection for Exchange (FOPE) spam filtering services.
The latest edition of Microsoft's security intelligence report provides a detailed breakdown of the various nefarious activities of the world's most noxious botnets. As well as providing a platform for spam distribution, many networks of compromised machines are used for phishing attacks, identity theft, click fraud and denial of service attacks.
Hall said that between April and June 2010, Microsoft cleaned botnet infections from more than 6.5 million computers worldwide. On Tuesday, Redmond added detection for the infamous Zeus crimeware Trojan to its malicious software removal tool, an application that cleans infection from compromised PCs and comes as an adjunct to Microsoft monthly Patch Tuesday security updates. ®