The Mobler worm doesn't have an automatic cross-platform spreading mechanism, but could be loaded by unwary users. It attempts to copy itself to all available media including USB drives and memory cards. On a Symbian device, it creates a Windows-executable installation package on the memory card. This can be seen by Windows Explorer when the device is connected to a PC.
F-Secure has put out an advisory on the virus and warns it is possible for users to accidentally infect the PC. Although not widespread, the virus was reported to it by an affected user, the company said.
Mobile malware has been slowly growing, with the first worm, Cabir, reported in 2004. Cabirspread from phone to phone by Bluetooth, describing itself as a software update. This method was also used by the Commwarrior Q worm, reported in August by F-Secure.
MMS messaging has also been used to spread between Symbian phones, by the Commwarrior A virus, reported in March 2005. Other mobile viruses have been spotted, including three in January.
Previous efforts to make a cross-platform mobile-to-PC virus include proof of concept bugs, such as Crossover reported in March. Last year, the Cardtrap A virus used the same crossover mechanism as Mobler.
So far, virtually all mobile viruses attack the Symbian operating system, as this is by far the most popular featured in smartphones.