Microsoft has released nine security updates for vulnerabilities in its software products, including three critical fixes for Windows and Internet Explorer. Among the updates is a patch for bugs in two separate components of the Windows operating system that security researchers believe could be exploited in by attackers in much the same way that the Zotob family of worms were used two months ago.

The software patches, called updates in Microsoft parlance, were released Tuesday as part of the company's monthly security software release. Two of the critical updates concern Internet Explorer and Microsoft's DirectShow media streaming software. A third update, described in Microsoft Security Bulletin MS05-051, concerns the COM+ services included with Windows as well as the Microsoft Distributed Transaction Coordinator (MSDTC), a component of the operating system that is commonly used by database software to help manage transactions.

It is these last two vulnerabilities that have security researchers concerned because of their similarity to the Windows Plug and Play (PnP) system vulnerability reported last August. Within a week of its disclosure, that flaw was exploited by the authors of the Zotob worm. Variations of this attack eventually knocked hundreds of thousands of machines offline, primarily affecting Windows 2000 users.

Microsoft has rated the MSDTC vulnerability as "critical" for users of Windows 2000, meaning the vulnerability could be used by attackers to seize control of any unpatched system. The COM+ bug is rated critical for Windows 2000 and Windows XP, Service Pack 1.

Security researchers say that another Zotob-style worm outbreak is now a possibility. "The COM+ and MSDTC vulnerabilities have a very similar appearance to the PnP vulnerability that caused Zotob," said Mike Murray, director of vulnerability and exposure research for security vendor nCircle Network Security.

Internet Security Systems' Neel Mehta, agreed that there were similarities between the PnP bug exploited by Zotob and MS05-051. "The scope of the affected platform is exactly the same and these services are run by default on Windows 2000," said Mehta, who is team leader of the company's X-Force research team. "In terms of ease of exploitation, they're not incredibly difficult to exploit, but they're not as easy as the Plug and Play vulnerability"

The IDG News Service is a Network World affiliate.