Microsoft informed Monday of a new vulnerability that influences IE users, saying that it could be broken by hackers to install malicious software on a user's computer.

The flaw deception in the way Microsoft's VBScript works with Windows Help Files in IE. But for an attack to work, the user should press the computer's F1 key, Microsoft said. "Our analysis shows that if users do not press the F1 key on their keyboard, the susceptibility cannot be exploited."

This kind of assault is considered harder to work out because of this F1 key must, but Web-based attacks have appeared as a most important source of malicious software over the past few years.

It affects Windows 2000, Windows XP and Windows Server 2003.

Microsoft has not seen the error broken in any online attacks to date, the company said Monday. Microsoft did not say whether it will fix the bug in its next set of security updates, due March 9, but it generally wants more than a couple of weeks to test and launch new security patches.