By Tom Espiner
May 16, 2008 7:17:56 AM

Microsoft has claimed user "complacency" is to blame for malware infections, and denied that its Vista operating system is less secure than Windows 2000. The claim that Vista is less secure than Windows 2000 was made last week by security vendor PC Tools, which said that over the past six months Vista had suffered 639 unique threats, whereas Windows 2000 has suffered 586.

PC Tools's research was conducted by collecting data from customers using its ThreatFire behavioral detection software. "Ironically, the new operating system has been hailed by Microsoft as the most secure version of Windows to date," said Simon Clausen, the chief executive of PC Tools last week.

"However, recent research conducted with statistics from over 1.4 million computers within the ThreatFire community has shown that Windows Vista is more susceptible to malware than the eight-year-old Windows 2000 operating system, and only 37 percent more secure than Windows XP," Clausen said. However, Microsoft strongly hit back at the claims, blaming users for executing malicious code on their machines. On Tuesday, Technet blogger and Microsoft evangelist Michael Kleef said the number of infections found by PC Tools was an indication of poor user behavior.

"The number of virus infections found by a virus vendor does not necessarily equal poor security," wrote Kleef in a blog post. "In many cases it equals poor user behavior. If I, despite all prompting and consent behavior, choose to go to a (probably dodgy) website, accept the ActiveX control prompts to download (probably dodgy) code and I actually choose to execute that code then I'm hosed."