Microsoft: Trojan Threat Significant, Rootkits Drop

New statistics from Microsofts anti-malware engineering team have confirmed fears that backdoor Trojans and bots present a "significant" threat to Windows users.

However, according to data culled from the software makers security tools, stealth rootkit infections are on the decrease, perhaps due to the addition of anti-rootkit capabilities in security applications.

The latest malware infection data, released Oct. 24 at RSA Conference Europe in Nice, France, covers the first half of 2006. During that period, Microsoft found more than 43,000 new variants of bots and backdoor Trojans that control millions of hijacked Windows machines in for-profit botnets.

Of the 4 million computers cleaned by the companys MSRT (Malicious Software Removal Tool), about 50 percent (2 million) contained at least one backdoor Trojan. While this is a high percentage, Microsoft notes that this is a decrease from the second half of 2005. During that period, the MSRT data showed that 68 percent of machines cleaned by the tool contained a backdoor Trojan.

Despite increased industry interest in Windows rootkits in 2005, Microsoft found a surprising 50 percent reduction in the attacks, which employ stealthy tricks to maintain an undetectable presence on infected computers. "This is a potential trend that will bear watching," the report said.

Microsoft believes the increase in anti-rootkit tools has helped to decrease the number of large-scale rootkit attacks in favor of more specialized techniques related to stealth.