Anti-virus vendors have spotted a new strain of the "Skulls" Trojan sneaking into Symbian-based cell phones, and this one drops the Cabir worm on the devices.

The latest mutant, Skulls.B, is similar to the Trojan discovered last week in the Nokia 7610 smart phone, which is powered by the Symbian operating system.

However, while the original "Skulls" Trojan simply disabled the smart-phone functionality on the handset, the new version also infects the device with Cabir, a worm that uses the Bluetooth protocol to copy itself onto devices as far as 30 feet away.