Threat description




Trojan:SymbOS/Fontal.C is a SIS file trojan that installs a corrupted Font file onto the device, causing it to fail to start at the next reboot.


Disinfection with two Series 60 phones

Please note that this disinfection method works only with phones on which the memory card can be changed without powering down the device.

Download F-Skulls tool ( or directly with clean phone (

1. Install F-Skulls.sis into infected phones memory card with a clean phone

2. Put the memory card with F-Skulls into infected phone

3. The F-Skulls starts automatically and frees the menu button and application manager

4. Press menu button until you get Symbian process menu, look for any applications with heart icon. Kill the application processes with 'C' button

5. Go to application manager and uninstall the SIS file in which you installed the Fontal.C

6. Download F-Secure Mobile Anti-Virus from and activate the Anti-Virus

7. Scan the phone and remove any remaining components of Fontal.C

8. Remove the F-Skulls with application manager as the phone is now cleaned

Disinfection for cases where phone is already rebooted and cannot start up

CAUTION! This method will remove all data on the device, including calendar and phone numbers.

1. Power off the phone

2. Hold following three buttons down "answer call" + "*" + "3"

3. Keep holding the buttons and power on the phone

4. Depending on the model, you either get text formatting or startup dialog that asks for initial phone settings

5. Your phone is now formatted and can be used again

Technical Details

Fontal.C also disables the application manager, application installer and messaging applications, which make its uninstallation more difficult.

If a phone is infected with Fontal.C, it must not be rebooted as the trojan will prevent the phone from booting again. If the phone is rebooted, it will try to boot, but will be forever stuck on phone startup and cannot be used without reformatting the phone.

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