F-Secure Virus Descriptions : Skulls.J

Summary

Skulls.J is minor variant of Skulls.D trojan. The main difference between Skulls.J and Skulls.D is that the Skulls.J doesn't drop any cabir variants directly. The Skulls.J drops SymbOS/AppDisabler.A trojan, which drops Cabir.Y and Locknut.B on the device.

In addition of dropping the AppDisabler.A the Skulls.J tries to disable F-Secure Anti-Virus and other Anti-Virus applications.

F-Secure Anti-Virus protected from the trojan attack as it is capable of detecting the trojan using generic detection, which was created long before this trojan surfaced.

Spreading in

Skulls.J trojan SIS file has been manually inserted into several different pirate copied games and applications. However none of these files have been detected in the wild.

Payload

Tries to disable Anti-Virus and drops SymbOS/Appdisabler.A.

Skulls.J also contains application that displays animation of flashing skull picture. But unlike in Skulls.D, Skulls.J does not contain startup code for the animation, this code is introduced by AppDisabler.A, but is prevented from working by Locknut.B which is also dropped by Appdisabler.A.

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Detection

Generic detection that detects Skulls.J was published for F-Secure Mobile Anti-Virus on December 13th, 2004 in database build number 15.

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Write-up: Jarno Niemela May 2nd, 2005;

F-Secure Corporation