Just in time for the festive season, a worm called Dasher has hit the internet. The malicious software, which primarily targets Windows 2000 systems, is one of three new attacks targeting Microsoft's software that has emerged in the last 24 hours.
Two other recently posted attacks can crash or slow down the Internet Explorer browser.
The first reports of Dasher began circulating on Thursday; Finnish security firm F-Secure has reported variants of the worm here.
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 as "critical" for Windows 2000 systems.
The worm's emergence does not come as a surprise. The 'proof of concept' code that could be used to make a worm such as 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 on Thursday. Both versions install software that then tries to infect other vulnerable systems, and that also can 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 percent," he said via instant message. "It fails 50 percent of the time."
However, he added that the worm still had the potential to infect thousands of systems.
Meanwhile, two IE exploits were posted to the Packet Storm website on Wednesday.
The first example takes advantage of a bug in the way IE processes CSS (Cascading Style Sheet) code, according to its author, Markus Heer. 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, said Heer, a developer with Penta, an IT consulting firm based in Switzerland. "I wrote the exploit after debugging the CSS/HTML code to find out the problem and develop a workaround for our application," he said.
A representative of 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.