07 April 2005

Fontal.A
New trojan that disables the phone so that it wont reboot

NAME: Fontal.A
ALIAS: SymbOS/Fontal.A

Fontal.A is a SIS file trojan that installs corrupted Font file into infected device, thus causing the device to fail at next reboot.

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.

Currently the only known way to disinfect a phone that is infected with Fontal and is rebooted is to reformat the phone, thus loosing all data on the phone.

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

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

After disinfecting you phone, you can remove remaining empty directories by going to 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

Spreading in Kill Saddam By OID500.sis

Infection

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

Exact detection for Fontal.A was published on April 6th, 2005 in database build number 35.

Write-up: Jarno Niemela April 6th, 2005;

F-Secure Corporation