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The Storm worm that wreaked havoc in January has opened up a new front in its war against users—instant messaging.
The Trojan virus that was responsible for countless spam e-mails sent around the globe has spawned a new variant that is using AOL Instant Messenger, Google Talk and Yahoo Messenger to proliferate. The worm attacks by detecting when someone is chatting and sending out a message with a link to the first stage of malware on a site. If the user clicks the link, the first stage will execute.
“The botnet handlers will periodically inject new commands into this peer-to-peer network, and one of the first things they do is tell the infected machines to download several executables,” explained Jose Nazario, software and security engineer for Arbor Networks, based in Lexington, Mass.
“These include updated binaries as well as several other components used for DDoS [distributed denial of service], spam, and additional spreading capabilities, and a rootkit to hide the malwares presence,” he continued. “The operators are constantly moving the machines to new network configurations to defeat firewalls and filters.”
The worm presents itself during an ongoing chat as an innocuous message such as, “Is it about you?”
“It is definitely smarter than the average bear,” said David Cole, director of Security Response at Symantec, in Cupertino, Calif. “Its really quite convincing.”
The worm was nicknamed Storm last month because it spread via e-mail with subject lines referring to major storms in Europe.
In addition, the worm also targets anti-spam Web sites, and even servers supporting rival malware with denial-of-service attacks, Nazario said. While it is not common for malware to attack one another, it has happened in the past, he said. The battle between Storm and Warezov—a mass-mailing worm that sends itself as e-mail attachments to addresses found on infected computers—is more external than malware-on-malware battles have been in the past, he said.
“Instead of targeting the same infected boxes, the authors are choosing to DDoS each others base of operations,” Nazario said. “They have also targeted high-impact DDoS events against anti-spam and anti-criminal efforts, such as Spamhaus. These two malware networks are built specifically for spam, it seems, and so anti-spam efforts go a long way to hurting their spam delivery efforts.”
Malware attacks using IM have been on the rise for the past few years. A research report by security software maker Akonix Systems, in San Diego, unearthed some 406 new IM-borne threats in 2006, compared with 347 attacks tracked by the company in 2005. Officials at the company predicted the number would increase in 2007 as well.
Nazario said the number of worms that are IM-specific appears to have leveled off; in their place however are multivector worms that know how to use instant messaging systems to propagate.
PC users can protect themselves from malware targeting IM systems in a number of ways. First, Nazario said, they should configure their IM clients to ignore messages from people not on their buddy lists. Secondly, they should practice the same kind of security there that they do for e-mail—treat unsolicited messages with suspicion.
“Sometimes asking someone to resend the link is enough to see that it was a machine sending the message and not a person,” he said. “All of this goes a long way towards defeating the simplest attack of all, the social engineering attack.”
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