REDMOND, WA – U.S. users of Windows-based computers are the primary targets of malware authors, according to the Microsoft Malware Protection Center. The software giant published a Top 10 list of countries besieged by malware on its blog earlier this week.“The U.S. is at the top of this list as it is by default the top target for most of the malicious code out there,” MMPC team members Marian Radu and Scott Wu wrote. “China and Brazil are actually a totally different story. While China is a top target for online games password stealers and the black market associated with it, Brazil is a prime goal for another breed of password stealers: those targeting bank accounts. Given these locations, it should come as no surprise that the top prevalent threats are what they are.”

During August, Microsoft’s Malicious Software Removal Tool was accessed 8.75 million times by U.S. users in order to clean 2.2 million machines, according to Microsoft’s records. The U.S. figures are larger than the combined numbers from the other nine countries on the list. In China, the second-most-often assaulted country, 1.09 million users employed the tool on more than 383,000 machines, and 1.08 million UK users cleaned more than 278,000 machines. PC users in Brazil, Korea, France, Taiwan, Spain, Canada and Mexico followed, in that order.

Radu and Wu explained the difference between the number of times the software tool was accessed and the number of machines cleaned represents multiple accesses by single users who either suffered infections by different malware families or endured re-infection of machines already cleaned at least once.

August’s top threats, according to Microsoft, included rogue anti-virus programs (malware masquerading as anti-virus tools), phishing worms that spread across mapped drives in order to make off with login and account info for online games, and data-stealing trojans.