This year saw Cabir, the first worm known to spread purely via wireless means, hit the wild, with scattered reports of infections of Symbian devices that had Bluetooth enabled.

Meanwhile, the Skulls Trojan, which masquerades as useful software but renders applications unlaunchable by replacing their icons, was also spotted on Nokia smartphones.

In the future, it is likely that we will also see new kinds of attacks: trojan horses in games, screensavers and other applications resulting in false billing, unwanted disclosure of stored information, and deleted or stolen user data, F-Secure said.

Most of the major antivirus vendors introduced mobile antivirus software during 2004, though the threat level is currently such that the software is not yet a must-have for mobile users.