New Version of MyDoom Worm in Zero-Day Attack

By Larry Seltzer  |  Posted 2004-11-09 Print this article Print

Buffer overflow in fully patched pre-SP2 Internet Explorer allows arbitrary code execution.

Anti-virus companies are reporting a worm that spreads via a new vulnerability in Internet Explorer. The vulnerability is not present in Windows XP Service Pack 2, but in all earlier versions of Internet Explorer 6, and no patch is available. It involves a buffer overflow triggered by an IFRAME or EMBED tag, which has an oversized SRC or NAME attribute.

What will be the next great worm? Find out here.
The worm, known as in McAfees naming, does not have a file attachment, as is typical of mail worms. Instead, it installs a Web server on Port 1639 of the infected system. The e-mails it sends out to spread itself contains a link to the server on the infected computer.

The page served when a user clicks the link, which takes the form http://aaa.bbb.ccc.ddd:1639/webcam.htm (where aaa.bbb.ccc.ddd is the IP address of the infected user), invokes the Internet Explorer vulnerability. The worm then takes over, downloading more files and spreading itself.

The use of an IP address means that users behind an NAT server cannot effectively spread the worm. Indeed, Ken Dunham, director of malicious code at iDefense Inc., said, "Home and SOHO users without sufficient perimeter defenses are most likely to be victimized."

For insights on security coverage around the Web, check out Security Center Editor Larry Seltzers Weblog. Most other anti-virus vendors are also terming the new worm a MyDoom variant, although Sophos plc. calls it Bofra-A. Vendors are generally terming this a low threat because it hasnt been seen in the wild, but some have elevated the threat because of the new techniques and the absence of a patch for the vulnerability.

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Larry Seltzer has been writing software for and English about computers ever since—,much to his own amazement—,he graduated from the University of Pennsylvania in 1983.

He was one of the authors of NPL and NPL-R, fourth-generation languages for microcomputers by the now-defunct DeskTop Software Corporation. (Larry is sad to find absolutely no hits on any of these +products on Google.) His work at Desktop Software included programming the UCSD p-System, a virtual machine-based operating system with portable binaries that pre-dated Java by more than 10 years.

For several years, he wrote corporate software for Mathematica Policy Research (they're still in business!) and Chase Econometrics (not so lucky) before being forcibly thrown into the consulting market. He bummed around the Philadelphia consulting and contract-programming scenes for a year or two before taking a job at NSTL (National Software Testing Labs) developing product tests and managing contract testing for the computer industry, governments and publication.

In 1991 Larry moved to Massachusetts to become Technical Director of PC Week Labs (now eWeek Labs). He moved within Ziff Davis to New York in 1994 to run testing at Windows Sources. In 1995, he became Technical Director for Internet product testing at PC Magazine and stayed there till 1998.

Since then, he has been writing for numerous other publications, including Fortune Small Business, Windows 2000 Magazine (now Windows and .NET Magazine), ZDNet and Sam Whitmore's Media Survey.

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