We are listing this threat as high to assure that people do not just ignore the level. Don't let themself fall pray to it.

Microsoft Corp. has released software that can be used to mitigate a critical vulnerability in Internet Explorer that was first reported last week.

The bug, which concerns the way Internet Explorer handles ActiveX components, can cause the browser to crash and could be used by an attacker to run unauthorized software on the user's machine, Microsoft said.

Yesterday, Microsoft released software that in the registry disables a file called Javaprxy.dll, which is used to run these components in Internet Explorer. This file is used by the Microsoft Java Virtual Machine, the company said.

Microsoft has not yet decided whether it will release a software patch that would fix the underlying problem, a spokeswoman said. "The work-around that they've offered here doesn't fix the underlying vulnerability, but it removes the functionality," she said.

Danish security company Secunia gave the vulnerability its most serious rating, calling it "extremely critical."

The Austrian security researchers who discovered the flaw expect Microsoft eventually to issue a full-blown patch.

"Right now, it's not that dangerous," said Martin Eisner, chief technical officer at security consulting company SEC Consult Unternehmensberatung GmbH. "But of course within a couple of weeks there will be somebody who has a little bit more time than we have and there will be an exploit then," he said in an interview last week.

Microsoft is unaware of any software that has exploited the bug, the spokeswoman said.

Microsoft has issued a security advisory that provides more details on the bug and lists other possible work-arounds to the problem.