Skulls.C is a variant of SymbOS/Skulls.A trojan, which has
similar functionality to the Skulls.A but uses different files.
Skulls.C is a malicious SIS file trojan that replaces the system
applications with non-functional versions, drops SymbOS/Cabir.F worm
in to the phone and disables third party applications that
could be used to disinfect with such as FExplorer, EFileman.
Skulls.C tries to disable F-Secure Mobile Anti-Virus by replacing it's
files with non-functional versions. However as F-Secure Mobile Anti-Virus
is capable of detecting Cabir.F contained by Skulls using generic detection.
The Anti-Virus will detect the infected SIS file and prevent it from being
installed. Provided that the Anti-Virus is in realtime scan mode as it is
by default.
The Cabir.F worm dropped by Skulls.C is already detected with generic
detection as Cabir.Gen. So the Skulls.C is already detected and stopped
without need for updated Anti-Virus database.
The Cabir.F dropped by Skulls.C does not activate automatically,
and will not activate on reboot. The only way the dropped Cabir
worm can activate is if user goes to the icon of the dropped Cabir
file and run it from there.
The Original Skulls.C SIS file is named "Skull.sis". Unlike Skulls.A,
the Skulls.C variant does not show any pop-up messages during install
(except the "Installation security warning - unable to verify supplier"
message shown by the operating system).
Like Skulls.A the Skulls.C replaces the application icons with skull
icon, this time so that each replaced application has caption "Skulls"
If Skulls.C is installed only the calling from the phone and answering
calls works. All functions which need some system application,
such as SMS and MMS messaging, web browsing and camera no longer function.
If you have installed Skulls.C, the most important thing is not to
reboot the phone and follow the disinfection instruction in this
description.
1. Install F-Skulls.sis into infected phones memory card with a clean phone
2. Put the memory card with F-Skulls into infected phone
3. Start up the infected phone, the application menu should work now
4. Go to application manager and uninstall the SIS file in which you installed the skulls variant
5. Download and install F-Secure Mobile Anti-Virus to remove any Cabirs dropped by the Skulls variant
http://www.europe.f-secure.com/estore/avmobile.shtml
or with mobile itself
http://mobile.f-secure.com
6. Remove the F-Skulls with application manager as the phone is now cleaned
Installation to system
Like Skulls.A Skulls.C is a SIS file that installs critical System ROM
binaries and Cabir.F worm into C: drive. The System ROM files
are installed with exact same names and locations as in the ROM drive.
Symbian operating system has a feature which causes any file that is
in C: drive replace file in ROM drive with identical name and location.
Spreading in
Skull.sis
Payload
Replaces built in applications with non-functional ones and installs
Cabir.F worm.
