"That said, we have always believed the measures Microsoft has taken in Vista is going to make it much harder for malware writers to create damage," he said.

Russ Humphreys, Microsoft product manager for Vista security, said the company is "evaluating" the information provided by Symantec, particularly issues in the operating system's GS Flag technology and its Address Space Layout Randomization feature.

"It is important to note that none of the security features in Windows Vista, either individually or collectively, are intended as a 'silver bullet' solution to the problem of computer security," Humphreys said in en e-mailed comment. "Instead, our defense-in-depth approach makes Windows Vista far more difficult to attack than any previous version of Windows, thus making it more secure." He said that Vista reflects a "right balance" between usability and security.

"This report does not properly address the fact that many of the Window Vista security technologies have numerous options that allow for a user to make their own judgments as to their need for security balanced against usability," he said.