Hackers hunting for unpatched Microsoft computers

IDG News Service - Hackers are actively using exploit code to target a flaw in Microsoft Corp.'s software that generated a special warning from the U.S. government last week (see "New Microsoft patch prompts DHS warning").

The problem involves a networking function called Windows Server services within the Windows operating system that is used for file sharing and printing.

Microsoft last week issued Patch MS06-040 for the problem, which affected several Microsoft operating systems. Security experts warned then that exploit code had been detected and could be used more widely.

However, the latest exploit code affects only users running Windows 2000 who have not applied the patch, Microsoft said. The effect so far from the malware, which the company calls "Win32/Graweg," has been minimal, the company said.

"We are not currently aware of widespread customer impact," Microsoft said Sunday.

The SANS Institute reported yesterday other names given to the exploit code by security vendors. Symantec Corp. calls it "W32.Wargbot," and TrendMicro Inc. has named it "Worm.IRCBOT.JK and JL." McAfee Inc. goes by "IRC.Mocbot," and F-Secure Corp. refers to the malware as "IRCBOT-ST."

The malware is a "bot," a class of malicious code that allows a hacker to take remote control over a computer. It appears to be a version of one called "Mocbot," which first appeared in late 2005, according to Lurhq Corp., a security company. Both SANS and Lurhq said two similar versions of the bot are circulating.

Once on an infected machine, the bot contacts remote servers in China over Internet Relay Chat, Lurhq said.

"Historically, Chinese [Internet service providers] and government entities have been less than cooperative in taking action against malware hosted and controlled from within their networks," Lurhq said in an advisory.

The bot is capable of several malicious functions, Lurhq said. It can send messages through a user's AOL LLC Instant Messenger account, an activity that could be used to trick other users into downloading the bot. The bot can also be used to launch a distributed denial-of-service attack, Lurhq said.

In addition, the bot could spread itself to other computers on a network, giving it worm-like characteristics. However, Microsoft said the exploit code does not appear to be self-replicating at this point.

The U.S. Department of Homeland Security highlighted the MS06-040 vulnerability a day after Microsoft issued a patch, saying it "could impact government systems, private industry and critical infrastructure, as well as individual and home users."

Microsoft issued a total of 12 fixes this month on what's known as "Patch Tuesday."