Viruses get smarter

Computerworld - He's been a virus writer for seven years. He goes by the handle Melhacker and may have been responsible for the recent outbreak of the Bugbear worm, the second most prevalent worm on the Internet last year. Now he claims to be working on a new virus, Scezda, that represents a new type of threat.

Scezda, as he describes it, falls into an emerging category of megaworms that combine features from some of this year's most prolific worms and viruses, including Sircam, Klez and Nimda. It uses a random number generator to determine how long it will remain dormant on a target system. Then it randomly chooses one of many different methods to replicate itself.

This is the essence of the new era of megaworms, what some experts refer to as blended, or polymorphic, threats that rely upon multiple methods of propagation. And that's just one way in which the virus threat is evolving.

Current Threats

Credit: David Hollenbach

Nine of the top 10 viruses detected by all major virus-protection companies in 2002 were mass-mailing viruses that exploited known vulnerabilities in the Win32 application programming interface. And 87% of all reports of infections stemmed from Windows viruses.

"Worms that are targeting known vulnerabilities are continuing to climb," says Vincent Weafer, senior director of the Symantec Security Response group at Cupertino, Calif.-based Symantec Corp. "That's significant because you're moving away somewhat from social engineering."

The most significant weakness exploited last year was the so-called malformed MIME vulnerability, originally discovered in 2001. Although a patch has been available for more than a year, viruses and worms have been able to capitalize on this vulnerability on unpatched machines to automatically execute a virus program when a user views an e-mail in preview mode.

Brid, Bugbear, Nimda and Klez all use this vulnerability, says Weafer.

"Today, the line between worms and viruses is blurred as successful designs take on characteristics of both and spread over the Internet," says Dan Ingevaldson, team leader of Internet Security Systems Inc.'s X-Force group. "The most successful worms act like a Swiss Army Knife, because they can spread by using many different proven methods, such as mass e-mail, Web server vulnerabilities or peer-to-peer technologies."

Virus Evolution

In the near future, companies will need to be prepared to deal with increasingly stealthy viruses carrying more destructive payloads, say researchers. In a recent research paper, Stuart Staniford, CEO of Silicon Defense in Eureka, Calif., outlined the emerging "threat of surreptitious worms that spread more slowly but in a much harder to detect 'contagion' fashion."