With disconcerting regularity, security firm F-Secure has discovered a number of Trojan viruses that target Symbian-based mobile devices.
The threats are the fifth such reported in recent months. Hobbes.A is a SIS file Trojan that looks like the Symantec Anti-Virus for the Symbian phones. When the Trojan is installed, it shows a dialogue instructing the user to reboot the phone in order to activate the Symantec Anti-Virus software.
The Trojan does not contain any antivirus software but a component that disables the phone's application menu. The Trojan has been tested in different phones and it seems to affect only the older Symbian Series 60 phones, such as NGage and 3650.
The Fontal.A Trojan is aimed at Nokia Series 60 phones that run on the Symbian operating system. The Trojan is spread through file sharing, with a corrupted font file being installed on the device. The .sis file is usually given the "Kill Saddam" tag and this file causes the mobile device to fail at the next re-boot. The only way for a user to get going again is to re-format the device to the original factory settings, meaning that they lose their personal data held on the phone.
F-Secure has warned users to only install files from trusted sources.