Phone Worm Source Code Out, Expect More Threats

The source code for the most prevalent worm targeting mobile phones has been made public, security firms announced Wednesday, a dangerous disclosure that may lead to more effective attacks.

Cabir, which first appeared in June, uses Bluetooth to infect smart phones running the Symbian operating system. Disguised as a security utility, Cabir itself doesn't do any permanent damage, but it has been used to deliver other malicious codes, such as the Skulls Trojan horse, to phones. The worm has been detected in several countries, including China, India, Turkey, the Philippines, and Finland, and spreads as people travel with infected phones. According to several anti-virus vendors, the source code for the Cabir worm is out and in the hands of those beyond the immediate circle of "29A," the Russian hacker gang thought responsible for originally creating the worm.

"As far as we know, until now the Cabir source code was accessible only to a limited number of people, including members of 29A," said Alecks Gostev, a senior virus analyst at Kaspersky Labs in an e-mail. "We think it was planned to publish the source code in the next edition of the group's electronic journal. [But] it looks like someone has already got access to the code, and now it's public.

"This will lead to a lot of new versions of Cabir," he added.

U.K.-based Sophos had a different take on the Cabir source code. The code, which Sophos has spotted on a Brazilian hacker's Web site, is not from 29A, but that used to create Cabir.h. and Cabir.i, the two most recent variations. According to Sophos, the Brazilian claims to have written the worms from scratch, then posted his own source code.

How it got there is less important than the fact it is there, said Sophos' senior technology consultant Graham Cluley in a statement.

"Publishing virus source code on the Web is dangerous because it encourages others to create malware. Although viruses for mobile phones have been creating more hype than havoc, it's possible that more malicious people will now be investigating ways to infect cellphones," he said.

Currently, Cabir's effects are limited to blocking normal Bluetooth connectivity and draining the infected phone's battery (since the worm repeatedly tries to connect to other Bluetooth devices to spread itself).

Helsinki-based security firm F-Secure noted in an online advisory that the new copies of Cabir -- Cabir.h and Cabir.i -- are more efficient than their ancestors at spreading.

"Cabir originally would only spread to one new phone per reboot, which explains why it so far has only managed to spread to eight countries despite being in the wild for months," F-Secure said in a statement issued Tuesday.

The new versions, on the other hand, can spread to an unlimited number of devices per reboot of the infected phone.

"As soon as a suitable target phone is seen, the worm sends itself and keeps sending itself to that phone while it is still in range," continued F-Secure. "Once the target phone leaves the area, Cabir.h and Cabir.i find a new target and continue spreading. In conditions where people move around and new phones come in contact with each other, Cabir.h and Cabir.i can spread rapidly."

While smart phones and handhelds have gotten away relatively unscathed in 2004, that probably won't continue, security firms have predicted.

"The increasing number of attacks shows that there's an interest building out there among the hacker community," said Symantec's Vincent Weafer in an interview last week. "As e-commerce becomes a bigger part of what people do with smart phones, so too will attacks."