Microsoft reported that its February security update for Windows XP and Vista has reduced the AutoRun abusing malware infection rates by as much as 82%.

In February Microsoft offered optional update to XP and Vista users, later it was changed to automatically download and install. The update was meant to disable AutoRun.

On Windows 7 system Microsoft changed AutoRun’s behavior to block automatic execution of files on a USB drive.

With the update introduced in February flash drives inserted into a PC running XP or Vista no longer offer the option to run programs.

According to statistics compiled by the MMPC from data delivered by the Malicious Software Removal Tool (MSRT), a free utility that detects and deletes some attack code, infection rates of malware that spreads through AutoRun plummeted after the February update reached XP and Vista.

Since January 2011, the month before the AutoRun update shipped, infection rates of XP Service Pack 3 (SP3) -- the sole version still supported by Microsoft -- have dropped by 62%. Vista SP1's infection rate has fallen by 68% while Vista SP2's has plunged by 82% in the same period.