Malicious code targets critical Windows flaw

Computer code that exploits a "critical" vulnerability in Windows has been released on the Internet, prompting Microsoft to issue a security advisory.

The attack code takes advantage of a flawed Windows routing and remote-access component for which Microsoft released a patch two weeks ago, the company said in its advisory published late Friday. The company is not aware of any cyberattacks that use the exploit code, it said.

"An attacker who successfully exploited this vulnerability could take complete control of the affected system," Microsoft said.

Microsoft urges users to apply the fix delivered with security bulletin MS06-025, which will remove the vulnerability. "We have confirmed that the exploit code does not affect users who have installed the update," Microsoft said.

However, the MS06-025 fix can interfere with certain dial-up networking connections, Microsoft said last week. The company advised people who use dial-up scripting or terminal window features not to install the security update while it works on a revised patch. That revision is still in the works, a Microsoft representative said on Monday.

The MS06-025 update was one of a dozen security bulletins that Microsoft released two weeks ago. At least one patch came after the vulnerability it addressed had already been exploited in a cyberattack. Exploits for some other flaws have also been released, further increasing the urgency to patch.