Threat Description

Trojan: SymbOS/Fontal.F


Category: Malware
Type: Trojan
Platform: SymbOS
Date Discovered: September 25, 2005
Aliases: Trojan:SymbOS/Fontal.F


Trojan:SymbOS/Fontal.F is distributed in a malicious SIS file named 'Nokia Update By 0ID500.sis'. On execution, the trojan installs a corrupted Font file onto the device, thus causing the device to fail to start at the next reboot.


Automatic action

F-Secure Mobile Security will detect Fontal.F and delete the trojan's components.

  • 1. Open web browser on the phone
  • 2. Go to
  • 3. Select link "Download F-Secure Mobile Anti-Virus" and then select phone model
  • 4. Download the file and select open after download
  • 5. Install F-Secure Mobile Anti-Virus
  • 6. Go to applications menu and start Anti-Virus
  • 7. Activate Anti-Virus and scan all files
More scanning & removal options

More information on scanning or removal options is available in the documentation for your F-Secure security product on the Downloads section of our Home - Global site.

You may also refer to the Knowledge Base on the F-Secure Community site for more assistance.


After disinfecting the phone, remove the remaining empty directories by going to the Application Manager and uninstalling the SIS file in which Fontal.F arrived (Nokia Update By 0ID500.sis).

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

If a phone is infected with Fontal.F, 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.


Suspect a file or URL was wrongly detected? Submit a sample to our Labs for analysis

Submit Now

Keep your mobile device protected

F-Secure Mobile Security will keep your mobile device protected on the go and enable you to find it in case you lose it

Learn More