Summary

MGDropper.B is a minor variation of MGDropper.A trojan that was found in December 2004.

Additional Details

MGDropper.B is a malicious SIS file dropper, that disables most well known third party file managers and Anti-Virus software, installs Cabir.X and drops MGDropper.A trojan.

The Cabir.X is started automatically when the MGDropper is installed and will start spreading. When Cabir.X spreads from MGDropper infected phone, the SIS files it sends will contain only the Cabir.X not MGDropper.

MGDropper.B 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.X contained by MGDropper 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.X worm dropped by MGDropper is already detected with generic detection as Cabir.Xen. So the MGDropper is already detected and stopped without need for updated Anti-Virus database.

Disinfection

Disinfection with two Series 60 phones

For full disinfection of MGDropper 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 ftp://ftp.f-secure.com/anti-virus/tools/f-skulls.zip or directly with phone http://www.europe.f-secure.com/tools/f-skulls.sis

1. Install F-Skulls.sis into clean 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. Install EFilemanager file manager application on your phone from http://www.psiloc.com
7. Insert the infected memory card into the phone and remove following files E:\System\Apps\SystemExplorer\SystemExplorer.app
E:\System\Apps\smartfileman\smartfileman.app
E:\System\Apps\file\file.app
E:\System\Apps\Anti-Virus\Anti-Virus.app
E:\System\Apps\Anti-Virus\FsAVUpdater.app
E:\System\Apps\AppInst\Appinst.aif
E:\System\Apps\AppInst\Appinst.app
E:\System\Apps\cabirfix\cabirfix.app
E:\System\Apps\Decabir\DECABIR.APP
E:\System\Apps\Disinfect\Disinfect.app
E:\System\Apps\FExplorer\FExplorer.app

Additional Details

Installation to system When installed MGDropper will replace most common third party file managers, Anti-Virus programs and application installer with non-functional versions.



Spreading in MetalGear_by_scar69.sis

Payload Drops MGDropper.A

Disables following applications

Simworks Anti-Virus
F-Secure Mobile Anti-Virus
Application installer
Cabirfix
Decabir
F-Cabir
FExplorer
File manager
Smart file manager
System Explorer

Detection

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


Write-up: Jarno Niemela June 15th, 2005;