Conficker gets upgraded with defenses

Anti-cabal resistance

Researchers at Symantec have discovered what could be a significant development in the ongoing Conficker worm saga: a new module that is being pushed out to some infected systems.

In a couple of ways, the new component is designed to harden infected machines against an industry consortium that is actively trying to contain the prolific worm. For one, the update targets antivirus software and security analysis tools to prevent them from removing the malware. Not only does it try to disable anti-malware titles, it also goes after programs such as Wireshark and regmon.

And for another, it also greatly expands the number of domain names infected machines contact on a daily basis.

Up to now, a pseudo random domain name generator produced 250 addresses that infected machines reported to each day. The industry consortium, dubbed the Conficker cabal, responded by cracking the algorithm and snapping up those domains ahead of the malware authors to prevent the infected machines from sustaining further damage.

The new component ups the ante by increasing the number of domains to 50,000 per day.

"It's clearly trying to work around the work of the cabal," Vincent Weafer, vice president of Symantec Security Response, told The Register.

So far, Symantec has been able to confirm delivery of the new component to only a handful of machines. Symantec researchers are in the process of determining if the updates are just the beginning of what will eventually be pushed out to infected machines everywhere, but either way, this appears to be the first time the malware authors have actually pushed out an update. Up to now the machines have phoned home but never received a reply.

"That's what makes this interesting, because this is what we believe is the first example of receiving an answer to that call," Weafer said. "Today is the very first case of that being successful."

Estimates of the number of machines infected by Conficker vary, from hundreds of thousands to more than 10 million. Weafer and other security researchers have said Conficker's growth has slowed over the past few weeks. That suggests its authors may be more focused on protecting the machines they've already vanquished than claiming new ones. ®

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