Singlejump.K is Symbian SIS file trojan that replaces system files and some third party applications with corrupted binaries from other symbian trojans. These components cause the device to reboot if executed and prevent the phone from booting, so if your phone is infected with Singlejump.K, it is critical not to reboot the phone. Singlejump.K also sends SymbOS/Mabir.A to the first device it finds over Bluetooth.


Disinfection with two Series 60 phones

Download F-Skulls tool from or directly to the phone from

  • Install F-Skulls.sis onto the infected phone's memory card with a clean phone
  • Put the memory card with the F-Skulls tool into the infected phone
  • Start up the infected phone and the application installer should work now
  • Go to the application manager and uninstall the SIS file in which you installed the malware
  • Download F-Secure Mobile Security and activate it
  • Scan the phone and remove any remaining components of the malware
  • Remove the F-Skulls tool with the application manager as the phone should now be clean

Disinfection for the cases when phone is already rebooted and cannot start up

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

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

Spreading in: Security+-+Application.SIS


Singlejump.K replaces built in and third party applications with components that cause the device to reboot if executed. The device will then fail to boot at that point.

Singlejump.K uses modified Cabir to spread other trojans. Instead of sending a copy of itself it loads SIS files installed by Singlejump.K and sends it to the first phone it finds within range of Bluetooth.

The above is the combined result of the different malware components dropped by Singlejump.K. These components are from following Trojans and viruses:

  • SymbOS/Doomboot.A
  • SymbOS/Appdisabler.Gen
  • SymbOS/Sendtool.A
  • SymbOS/Singlejump.C
  • SymbOS/Fontal.A
  • SymbOS/Blankfont.A
  • SymbOS/Mabir.A

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