New variants of Zotob worm found

Antivirus vendors reported new variants of the Zotob worm, but the outbreak appears less severe than first feared.

Security vendors have reported several new variants of the worm infecting PCs running Microsoft's Windows 2000 operating system. Groups of virus writers are competing to cause the most damage, according to one security company, although the worm appears less severe than some first feared.

F-Secure said on Wednesday that it had identified three "families" of worms -- Zotob, Bozori and Ircbot -- all stemming from a vulnerability reported Aug. 9 in Microsoft's Windows 2000 Plug and Play software. The worm will cause infected systems to continually reboot, antivirus vendors said.

The Finnish security company has seen 11 variants of the worms altogether, including four that appeared Wednesday morning in Europe, said Mikko Hypponen, F-Secure's chief research officer.

The extent of the damage is hard to measure, he said, but the worm does not appear to be as serious as the Sasser or Blaster worms of recent years, in part because it does not affect the more widely used Windows XP operating system.

Still, it is the worst virus outbreak so far this year, Hypponen said. A "botwar" appears to have broken out in which three virus-writing "gangs" are competing to create a worm variant that causes the most damage, he said. The latest variants of the Bozori worm are even removing "competing" viruses from users' machines, according to F-Secure.

The worms affect only Windows 2000 computers, Microsoft and antivirus vendors said. Microsoft released a patch for the Plug and Play vulnerability (MS05-039) on Aug. 9, but home users are notoriously slow to patch their machines, and some businesses have been reluctant to do so for fear of "breaking" custom applications, security experts said.

On Tuesday, Microsoft contested reports that any new viruses have emerged, saying all the worms are variants of Zotob. It continued to rate the issue as "a low threat for customers," and said it had seen only low rates of infection. Still, it ranked the original flaw in its software as "critical."

However, McAfee's antivirus response team raised its risk assessment to "high" for one variant of the IRCBot worm. Late Tuesday it said it had received more than 150 reports of the worm either being stopped or intercepting users' PCs, mostly in the U.S. but also from Europe and Asia.

Trend Micro Inc. received reports of infections from three corporate customers, which it considers a low level, a spokesman for the company in Tokyo said Wednesday. None of the reports were from major corporations, he said.

Media outlets have been among the hardest hit by the worm, including Time Warner's CNN news network, The New York Times and the ABC television network, a unit of The Walt Disney Co., according to a report in Wednesday's Wall Street Journal newspaper.

This may be because one of the variants, Zotob.C, can masquerade as a picture file, suggested Alan Paller, director of Research at The SANS Institute.

"If an early infectee had an email list with reporters at all the major news services, that would start the cascade. News organizations do not have radical email attachment limits (like a rule banning all picture attachments) because they get legitimate pictures," Paller wrote in an e-mail.

The IRCBot worm first appeared seven days after the Microsoft vulnerability was first reported, marking the fastest time to create a mass propagating exploit, McAfee said. The first successful mass exploit for the Sasser worm took two weeks to appear, the company said.

Infections continued to be reported at large organizations, especially in the U.S., F-Secure said. These most likely stemmed from laptops carried inside the organizations' perimeter firewall, it said.

The worms replicate by scanning machines at port 445/TCP and, when a victim is found, use the exploit code to download the main virus file via FTP (file transfer protocol). The virus then sets up an FTP server on the infected machine and starts scanning for more targets to spread.

The extent of the damage is hard to measure because the worms do not spread via e-mail, Hypponen said.

Microsoft released the patches Aug. 9. The next day, a Russian individual using the name "Houseofdabus" released working exploit code that could be used to take over machines that have the vulnerability, F-Secure said.

By Sunday, the Zotob.A worm was found. An unknown party had incorporated the Houseofdabus code into a worm that would spread automatically over the Internet, F-Secure said. A similar development occurred in May last year, it noted, when virus writer Sven Jaschan incorporated Houseofdabus' LSASS exploit code into his Sasser worm.

As usual, the worm outbreak kept antivirus vendors working through the night. Hypponen had been up since 2 a.m. and was about to eat for the first time on Wednesday afternoon, he said.

Microsoft's Web page, "What you should know about Zotob," includes links to the patch and was updated Tuesday at http://www.microsoft.com/security/incident/zotob.mspx

Symantec has information at

McAfee has information at

F-Secure has information at http://www.f-secure.com/v-descs/zotob_a.shtml

(Martyn Williams and Robert McMillan contributed to this story.)

Join the newsletter!

Or

Sign up to gain exclusive access to email subscriptions, event invitations, competitions, giveaways, and much more.

Membership is free, and your security and privacy remain protected. View our privacy policy before signing up.

Error: Please check your email address.
Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

James Niccolai

IDG News Service
Show Comments

Brand Post

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Luke Hill

MSI GT75 TITAN

I need power and lots of it. As a Front End Web developer anything less just won’t cut it which is why the MSI GT75 is an outstanding laptop for me. It’s a sleek and futuristic looking, high quality, beast that has a touch of sci-fi flare about it.

Emily Tyson

MSI GE63 Raider

If you’re looking to invest in your next work horse laptop for work or home use, you can’t go wrong with the MSI GE63.

Laura Johnston

MSI GS65 Stealth Thin

If you can afford the price tag, it is well worth the money. It out performs any other laptop I have tried for gaming, and the transportable design and incredible display also make it ideal for work.

Andrew Teoh

Brother MFC-L9570CDW Multifunction Printer

Touch screen visibility and operation was great and easy to navigate. Each menu and sub-menu was in an understandable order and category

Louise Coady

Brother MFC-L9570CDW Multifunction Printer

The printer was convenient, produced clear and vibrant images and was very easy to use

Edwina Hargreaves

WD My Cloud Home

I would recommend this device for families and small businesses who want one safe place to store all their important digital content and a way to easily share it with friends, family, business partners, or customers.

Featured Content

Product Launch Showcase

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?