Microsoft has just released vulnerability data collected from its Malicious Software Removal Tool (MSRT), Bing, Windows Live Hotmail, Forefront and Defender during the first half of this year.
Windows XP SP3 remains the most vulnerable OS among the currently still-supported Microsoft operating systems. The data released show that 10.9 of every 1000 Windows XP SP3 (32-bit) were infected during the first half of the year. In comparison, the number dropped to 8.8 for Vista SP1 32-bit (6.7 for 64-bit), to 5.7 for Vista SP2 (4.4 for 64-bit) to 4.0 for Windows 7 RTM (2.7 for 64-bit) and to 1.8 for Windows 7 SP1 (1.1 for 64-bit).
Malware is most commonly distributed via adware with a share near 24 percent, followed by "unwanted" software (20 percent) and trojans (18 percent), worms (12 percent) and trojan downloaders (10 percent). Spyware has become insignificant as a malware transportation vehicle.
Microsoft detected most of the malware infections in the U.S. (10.5 million in Q2). Brazil was second with 3.7 million and France third with 2.7 million compromised Windows systems.
Microsoft's Security Intelligence Report v11 can be downloaded from Microsoft's website.