The battle against 'Autorun' malware, once a major threat to PC users, appears to be heading for victory according to new figures put out by Microsoft that show big declines in infection rates during 2011.
Between January and May 2011, the number of Autorun-related malware infections detected by Microsoft's Malicious Software Removal Tool (MSRT) dropped 59 percent on XP machines and 74 percent on Vista, compared to the levels seen in 2010, equivalent to a 1.3 million drop.
The transformation appears to date from the retrofitting in January of this year of security that allowed the Autorun feature to be turned off on Windows XP and Vista for risky media such as USB sticks but not for others such as C Ds and DVDs. Windows 7 shipped with this feature and so wasn't included in the analysis.
"It's not every day that you have such strong confirmation that something you were a part of made a difference in the world, but I have to say that seeing 1.3 million fewer infections over the past few months and all of these trend lines going down - that just feels good," said Microsoft's Holly Stewart in a blog post.
Infection levels from this form of malware would probably never reach zero because some of it can infect PCs through other routes, she said.
Examples of Autorun malware, which spread by executing automatically when media such as USB sticks are connected to a PC, are legion.
The best-known example of Autorun malware is probably the Conficker worm, which appeared to some consternation in 2008, but Microsoft has also tracked Taterf, Rimecud, and a large generic category of unknowns labelled simply 'Autorun', all of which are now at all-time lows.