Blankfont.B

Threat description

Details

Category: Malware
Type: Trojan
Platform: SymbOS
Aliases: Blankfont.B

Summary


Trojan:SymbOS/Blankfont.B is a SIS file trojan that installs corrupted system binaries/font file. The system files dropped by Blankfont.B cause the device to fail on the next reboot. If you have installed Blankfont.B, the most important thing is not to reboot the phone and follow the disinfection instructions in this description.



Removal


Disinfection

  • Uninstall the SIS file with which Trojan:SymbOS/Blankfont was installed
  • To make sure that uninstallation was successful, scan your phone with antivirus before rebooting the phone

Disinfection for cases when the phone has been rebooted

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

  • Power off the phone
  • Hold following three buttons down "answer call" + "*" + "3"
  • Keep holding the buttons and power on the phone
  • Depending on the model, you either get text "formatting" or start-up dialog that asks for initial phone settings
  • Your phone is now formatted and can be used again

Prevention

Protect your mobile device with F-Secure Mobile Security.



Technical Details


Trojan:SymbOS/Blankfont copies corrupted font files into the phone's memory and thus prevents the phone from loading the valid font files from ROM.

The corrupted font file installed to the phone does not cause device to crash, but if the device is rebooted it will then lose the system font and is unable to display user interface texts.

Installation to the System

Blankfont.B installs corrupted system binaries into the C:\ drive of the phone. When the phone boots these corrupted binaries will be loaded instead of the correct ones, and the phone will crash at boot.



Detection


F-Secure Mobile Anti-Virus for Symbian detects this malware starting from the update build number 45.




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