On Dasher! New malware targets Microsoft users

IDG News Service - Just in time for the holidays, a worm called Dasher has hit the Internet. The malicious software, which primarily targets Windows 2000 systems, is one of three new attacks that have emerged in the past 24 hours targeting Microsoft Corp.'s software. Two other recently posted attacks can crash or gum up Microsoft's Internet Explorer browser.

The first reports of Dasher began circulating today, and two variants of the worm have now been reported by Helsinki, Finland-based security firm F-Secure Corp.

Dasher is based on an exploit for a recently patched bug in Microsoft Distributed Transaction Coordinator, a component of the operating system that is commonly used by database software to help manage transactions. Microsoft rates the bug "critical" for Windows 2000 systems.

The worm's emergence doesn't come as a surprise. The proof-of-concept code that could be used to make a worm like Dasher first began circulating after Microsoft issued its patch in early October. Some security researchers feared that it could be used to create a worm similar to last August's Zotob attack, which brought down hundreds of thousands of systems worldwide.

Two variants of Dasher are now in circulation, F-Secure said today. Both versions install software that then tries to infect other vulnerable systems and can also be used to log keystrokes and turn the computer into a remotely controlled "bot" system.

One version of the worm seems to be largely ineffective thanks to some buggy code, and other variations are unlikely to be as widespread as Zotob, said Cesar Cerrudo, CEO of security research firm Argeniss in Parana, Argentina. "I don't think it will be a successful worm, since that vulnerability is difficult to exploit 100% ... it fails 50% of the time," he said via instant message. However, he added, the worm still has the potential to infect thousands of systems.

Meanwhile, two Internet Explorer exploits were posted to the Packet Storm Web site on Wednesday.

The first example takes advantage of a bug in the way Internet Explorer processes Cascading Style Sheets code, according to its author, Markus Heer, a developer at Penta Group, an IT consulting firm in St. Gallen, Switzerland. CSS is a formatting standard used to give Web pages a consistent look and feel.

The bug was discovered during the course of building an enterprise Java application, Heer said in an e-mail interview. "I wrote the exploit after debugging the CSS/HTML code to find out the problem and develop a workaround for our application," he said.

The second exploit, attributed to a hackernamed "Ziplock," exploits a JavaScript bug to lock up an Internet Explorer browser. Both this and the CSS code have been tested and found to work with Version 6.0 of Internet Explorer, the hackers said.

A representative at Microsoft's public relations agency was not able to comment on the bugs, and an executive at the company responded to an interview request by saying he would look into the matter and comment when he had more information.

Reprinted with permission from

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