Security tests prodding Microsoft's Windows Vista operating system for vulnerabilities have found it is 37 percent more secure than its predecessor, Windows XP.

You'd think this finding would be good news for Microsoft, but it isn't, according to the security firm PC Tools [1], which performed the test using its anti-malware software, ThreatFire [2].

PC World explains [3]:

"We wanted to find out how bulletproof Vista was," said [Michael] Greene [vice president of product strategy for the security firm, PC Tools, which produces ThreatFire], noting that Microsoft has claimed Vista is significantly more secure than its predecessors. "The answer is that it is more secure than XP, but not so secure that you can give up on anti-virus and other security software." 

When conducting their test, PC Tools found 639 unique threats for every 1,000 computers running the Vista operating system over a six-month period. In contrast, the firm found 1,021unique threats for every 1,000 computers running the almost seven-year-old XP operating system.

A unique threat was only counted when malware was found on the computer, says Green.

"I didn't think the situation would be this bad in general," Green told PC World, adding that Microsoft's claims that Vista is substantially more secure than XP doesn't jibe with the ThreatFire numbers.

Using its own software called the Malicious Software Removal Tool [4](MSRT), Microsoft reported three weeks ago that Vista was 60 percent more secure than XP. To read that report, go here [5].