Threat description




Singlejump.F (renamed Onehop.F) is Symbian SIS file trojan that replaces system files and some 3rd party applications with corrupted binaries from SymbOS/Doomboot.A trojan. These components prevent phone from rebooting, so if your phone is infected with Singlejump.F, it is critical not to reboot the phone or click any changed icons. Singlejump.F sends also SymbOS/Singlejump.B to the first device it finds with Bluetooth.


Disinfection with two Series 60 phones

For full disinfection of Singlejump.F you need help of another Series 60 phone that is not infected with the trojan, and clean memory card on that phone.

Download F-Skulls tool from or directly with phone

  • Install F-Skulls.sis into clean phones memory card with a clean phone
  • Put the memory card with F-Skulls into infected phone
  • Start up the infected phone. The application menu should work now
  • Go to application manager and uninstall the SIS file in which you installed the skulls variant
  • Download and install F-Secure Mobile Anti-Virus to remove any Cabir variants from or with mobile from
  • Insert the infected memory card into the phone and remove installed files
Disinfection for the 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

  • 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

Technical Details

Installation to system

When installed Singlejump.F will replace most common third party file managers and application installer with non-functional versions. Some icons are also replaced with application that causes device to reboot.


Singlejump.F replaces built in and third party applications with component that causes reboot to fail.

Singlejump.F use modified Cabir to spread other trojans. Instead of sending a copy of itself it loads SIS file installed by Singlejump.F and sends it to the first phone it finds within Bluetooth range. In most cases these trojans doesn't send themselves further.


F-Secure Mobile Anti-Virus for Symbian detects this malware starting from the

Detection Type: Mobile

Database: update build number 15

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