Source code for the most prevalent worm targeting mobile phones has been made public -- potentially encouraging worse attacks.
Global security firms said yesterday that the source code for the Cabir worm had been released into the wild and was believed to be in the hands of those beyond the immediate circle of 29A, a Russian hacker gang thought responsible for creating the worm.
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 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.
"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 Russia-based Kaspersky Labs.
"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.
However, UK-based security firm Sophos said it had seen Cabir source code on a Brazilian hacker's website that was not from 29A. That code was used to create Cabir.h. and Cabir.i, the two most recent Cabir variations.
The Brazilian hacker claimed to have written the worms from scratch then posted his own source code, Sophos said.
But how it got there was less important than the fact it was 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 more malicious people will now be investigating ways to infect mobile phones," Cluley said.
Cabir's effects had been limited to blocking normal Bluetooth connectivity and draining the infected phone's battery. The worm tries repeatedly to connect to other Bluetooth devices to spread itself.
Finland-based security firm F-Secure noted in an online advisory that the new copies of Cabir -- Cabir.h and Cabir.i -- were 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 28 December.
The new versions, on the other hand, could 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," wrote 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 had got away relatively unscathed in 2004, that probably would't continue.
"The increasing number of attacks shows that there's an interest building out there among the hacker community," said Symantec security response director Vincent Weafer. "As e-commerce becomes a bigger part of what people do with smart phones, so too will attacks."