Trojan:SymbOS/Fontal.B, SymbOS/Fontal.B


Trojan:SymbOS/Fontal.B is distributed in a malicious SIS named 'Nokia Anti-Virus.sis', which claims to be "Nokia Anti-Virus for Symbian" devices.

Automatic action

F-Secure Mobile Security will detect Fontal.B 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


After disinfecting your phone, you can remove remaining empty directories by going to the application manager and uninstalling the SIS file in which Fontal.B arrived (Nokia Anti-Virus.sis).

Disinfection for cases when 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 fomatted and can be used again

Suspect a file is incorrectly detected (a False Positive)?

A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:

  • Check for the latest database updates

    First check if your F-Secure security program is using the latest detection database updates, then try scanning the file again.

  • Submit a sample

    After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.

    NOTE If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.

  • Exclude a file from further scanning

    If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.

    Note You need administrative rights to change the settings.

For more Support


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User Guide

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Submit a sample

Submit a file or URL for further analysis.

Technical Details

When installed, Fontal.B will show the following installation text:

Nokia Anti-Virus keep your phone protected from mobile virus. Please restart
your phone after installation complete to activate your anti-virus product.
If you found any problem regarding this software, please call :

If a phone is infected with Fontal.B, 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.


When the Fontal.B SIS file is installed the installer copies files into following locations:

  • \apps\KAS
  • \apps\KAS\b.dat
  • \apps\KAS\Engine.exe
  • \apps\KAS\KAS
  • \apps\KAS\KaS.aif
  • \apps\KAS\KAS.r01
  • \apps\KAS\KAS_caption.r01
  • \apps\KAS\klnotify.rsc
  • \apps\KAS\limages.mbm
  • \apps\KAS\
  • \apps\KAS\lnotify.mbm
  • \apps\KAS\s.mid
  • \help\KasAntivirusHelp.hlp
  • \libs\kasdll.dll
  • \recogs\kas_antivirus.mdl
  • \system\Fonts\Kaspersky