Exploit Code Discovered for New Microsoft Flaw

SAN FRANCISCO-- Security assessment vendor Immunity has discovered a way to exploit a recently disclosed bug in Microsoft's Windows operating system, and researchers are concerned that a new worm attack, similar to last August's Zotob outbreak, may be imminent.

The bug, which Microsoft patched on Tuesday, primarily affects users of Windows 2000, the same operating system that was targeted in the Zotob attacks. It concerns the Microsoft Distributed Transaction Coordinator (MSDTC), a component of the operating system that is commonly used by database software to help manage transactions.

Microsoft this week rated the vulnerability as critical for Windows 2000 users and said that, if exploited, it could be used to seize control of an unpatched system.

Immunity's Involvement

Late Tuesday, just hours after Microsoft disclosed the vulnerability, Immunity began distributing the exploit to members of the company's Immunity Partners program, which is composed primarily of security researchers, says Justine Aitel, the company's chief executive officer. The code will be included in the next release of the company's Canvas security assessment software, scheduled for release on November 1, she adds.

"Right now we have a proof of concept for that particular vulnerability," Aitel says. "The vulnerability can be exploited."

Immunity's proof-of-concept release makes it more likely that hackers will begin targeting the same bug, says Neel Mehta, team leader of the X-Force research team with Internet Security Systems.

"The fact that they created an exploit for it will spur other hackers to go ahead and do the same, knowing that it's possible," he says.

Based on its own research, ISS believes that the bug may enable a fairly widespread Windows 2000 worm, Mehta says. "It can be very reliably exploited, and it has the potential to be another worm," he says.

Microsoft executives were not available to comment on this matter, but the company released a statement saying that it was "not aware of any active attacks that use this exploit code."

Corporate Servers at Risk

Though Microsoft is encouraging all Windows 2000 users to install its software patch, security experts say the problem may be more acute for Windows Server 2000 customers than it is for users of the Windows 2000 Pro client software. This is because the MSDTC service is turned on by default on the server software, but turned off by default on the client, according to Microsoft.

Though consumer users have largely moved on to Windows XP, which is not considered nearly as vulnerable to this attack, Windows 2000 is still widely used in corporate environments. And as the Zotob attacks proved two months ago, attacks that focus on the older operating system can still be fairly disruptive.

Zotob exploited a vulnerability in the Windows Plug-and-Play system, and variations of the worm disrupted hundreds of thousands of Windows 2000 machines at companies like American Express and Cable News Network.

More details on the MSDTC bug, including Microsoft's patch, can be found in Microsoft Security Bulletin MS05-051.