A strain of mobile malware targeting Symbian-based phones is "actively infecting" a small number of smartphones, according to security vendor Fortinet.

The worm, dubbed Beselo-A, is capable of infecting Symbian S60 devices including, but not limited to, a range of Nokia smartphones (Nokia 6600, 6630, 6680, 7610, N70, and N72 handsets). The malware is disguised as a multimedia file with names such as Beauty.jpg, Sex.mp3, or Love.rm. Installing these files on devices running Symbian results in an infected smartphone.

After infection, the worm harvests phone numbers located in a user's contacts lists and targets them with a viral MMS message carrying a SIS-packed (Symbian Installation Source) version of the worm. The malware also sends itself to mobile numbers located in China and to a particular mobile phone operator.

If this is part of a money making scam then it's a well disguised one. Fortinet reports that some of these numbers have been verified to belonging to actual customers, rather than being associated with premium rate numbers.

Fortinet is investigating the attack. As with previous mobile malware outbreaks, incidents of infection from the low-risk worm are rare. ®