Security firm Fortinet says a mobile phone worm written for the Symbian OS has been found in the wild.
The threat, a viral MMS called the SymbOS/Beselo.A!worm, has been "actively spreading on various mobile phone networks," the company said without elaborating.
It can run on Symbian S60 devices, such as the Nokia 6600, 6630, 6680, 7610, N70 and N72 phones.
After installation, the worm harvests phone numbers in the contact list and targets them with a viral MMS carrying a SIS-packed (Symbian InstallationSource) version of the worm, usually disguised as a multimedia file named Beauty.jpg, Sex.mp3 or Love.rm.
The worm also sends itself to some China mobile numbers, some of which belong to actual customers. "The whys and hows of such a routine are still under Investigation," Fortinet said.
It said users would know they have been infected if they see unrecognized sent messages in their MMS outboxes.