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Trojan:SymbOS/Fontal.A


Discovered:
Aliases:


April 06, 2005
Trojan:SymbOS/Fontal.A

Malware
Trojan
SymbOS

Summary

Also known as a trojan horse program, this is a deceptive program that performs additional actions without the user's knowledge or permission. It does not replicate.



Disinfection & Removal


Automatic Disinfection

F-Secure Mobile Anti-Virus will detect Fontal.A and delete the trojan's components.

  • 1. Open web browser on the phone
  • 2. Go to http://mobile.f-secure.com
  • 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

Note

After disinfecting the phone, remove the remaining empty directories by going to the Application Manager and uninstalling the SIS file in which Comwarrior arrived (Kill Saddam By OID500.sis).


Manual disinfection

1. Install file manager on the phone

2. Go to c:\System\apps\appmngr

3. Delete appmngr.app

4. Go to the application manager

5. Uninstall the SIS file in which the Fontal.A was installed in


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.

  • 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


Technical Details

Trojan:SymbOS/Fontal.A is distributed in a malicious SIS file named 'Kill Saddam By OID500.sis'. If executed, it installs a corrupted Font file onto the device, causing the device to fail at next reboot.

In addition to installing the corrupted font file, Fontal.A also damages the application manager so that it cannot be uninstalled. No new applications can be installed before the phone is disinfected.

If a phone is infected with Fontal.A, 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.


Execution

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

  • \system\apps\appmngr\appmngr.app
  • \system\apps\kill sadam\kill sadam.app
  • \system\apps\fonts\kill sadam font.gdr

The appmngr.app is a non-functional file that disables the application manager; the kill sadam.app is a hexedited utility that has been modified to show text reboot and has no other significant function for the trojan.







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