BeyondTrust Corp. , which touts its Privilege Manager as a way for companies to lock down PCs, tallied the individual vulnerabilities that Microsoft disclosed in 2008, then examined each accompanying security bulletin. If the bulletin's "Mitigating Factors" section, the part that spells out how to lessen the risk of attack or eliminate it entirely, said that users with fewer rights "could be less impacted than users who operate with administrative rights," BeyondTrust counted the bug.

The vast majority of critical Microsoft vulnerabilities -- 92% of them -- could have been mitigated by stripping users of administrative rights, said John Moyer, the CEO of BeyondTrust. "This speaks to what enterprises should be doing," Moyer said. "Clearly, eliminating administrative rights can close the window of opportunity of attack."

Of the 154 bugs published and patched by Microsoft in 2008, critical or not, 69% would have been blocked or their impact reduced by configuring users to run without administrative rights, said the company.

When BeyondTrust looked at the vulnerabilities patched for Microsoft's browser, Internet Explorer (IE), and its application suite, Office, it found that 89% of the former and 94% of the latter could have been stymied by denying users administrative privileges.

"We were surprised to see how large the number was," said Scott McCarley , the company's director of marketing. "It really drives home how critical a role [rights] play."

Microsoft's approach to user rights has been a matter of debate of late. Last week, a pair of bloggers posted proof-of-concept code that demonstrated how attackers could disable Windows 7's revamped User Account Control (UAC) . UAC, a security feature that debuted in 2007 with Windows Vista, prompts users for their consent before Windows allows tasks such as program installations to continue.

"That proof-of-concept illustrates how important it is that users log in as a standard user, not as administrative users," said McCarley. Only users running Windows with administrative rights are vulnerable to the attack.

Microsoft has refused to call the Windows 7 UAC issue a security bug, and instead has insisted that the behavior exploited by the malicious script is by design.