What Windows Autorun Has Wrought

Brian Krebs
WashPost Security Fix

A new report by Microsoft shows that the two most prevalent threats to Windows PCs in the first half of 2009 were malicious programs that have been aided mightily in their spread by a decision by Microsoft to allow the contents of removable media -- such as USB thumb drives -- to load automatically when inserted into Windows machines.

In its latest "Security Intelligence Report," Microsoft counted the number of threats detected by its anti-malware desktop products, and found that the Conficker worm, along with a Trojan horse program called Taterf which steals passwords and license keys for popular computer games, were detected on 5.21 million and 4.91 million Windows computers, respectively.

The original version of Conficker emerged nearly a year ago, and initially it spread by exploiting a networking vulnerability in Windows. But Conficker infections soared by the millions in January with the arrival of Conficker B, which introduced the ability to spread via the Autorun capability in Windows. Taterf spreads exclusively via Autorun.

Together, these two threats accounted for more than 35 percent of the top 10 malicious software infections in first six months of this year, Microsoft found (click the chart below for a breakdown of those threats). According to the previous Security Intelligence Report, more than 17 percent of infections in the second half of 2008 were by malware that can spread via AutoRun.

(Original with download links is here.)