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Worm.Zimuse.A

VERY LOW
VERY HIGH
aprox 195Kb
(Trojan.Startpage.G, Win32/Zimuse.A, Worm:Win32/Zumes.A!sys)

Symptoms

      Presence of the following files
        * %system32%\drivers\mstart.sys
        * %system32%\drivers\mseu.sys

Removal instructions:

Please let BitDefender disinfect your files. For more information please visit Zimuse website.

Analyzed By

Daniel RADU, Senior Virus Researcher

Technical Description:

       The malware comes as an application with a WinZip icon in order to trick the user into running it. To look even more as a a self-extracting archive it displays a dialog box asking for a password in order to successfully unzip the package contents.

      Once executed the application checks the command line parameters and if there is a switch '/Z' then it proceeds to delete all the files , all the registry keys it and all the services it has created during a previous infection. 

      If no disinfection switch is given then it takes the following actions:
      * it checks if it's set to run at startup up, by checking the presence of a key named 'Dump' in HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run.
      * if no previous infection is found then it infects the computer.

      Infection of the computer consists in:
         * dropping the  files
             - %system32%\drivers\mstart.sys and creates and runs a service named 'mstart' from this file;
             - %program-files%\Dump\dump.exe"
             - %Temp%\Dump.ini
             - %Temp%\Regini.exe
             - %system32%\drivers\mstart.sys
             - %system32%\drivers\mseu.sys
             - %Temp%\mseu.ini (used for installation of mseu.sys service)
             - %system32%\mseus.exe
             - %Temp%\mseus.ini (used for installation of mseus.exe service)
             - %system32%\tokset.dll
             - %system32%\ainf.inf
             - %Temp%\instdrv.exe (which is a clean file used to install services)
             - %system_drive%\IQTest\iqtest.exe (in some versions)
             - %system_drive%\IQTest\readme.txt (in some versions)

         * sets dump.exe file dropped earlier to run at startup (this is the flag of infection)
         * deletes the following files (which were used for services instalation)
             - %Temp%\Regini.exe
             - %Temp%\Dump.ini 
             - %Temp%\mseu.ini
             - %Temp%\mseus.ini
             - %Temp%\instdrv.exe

       The malware is inactive for the first 10 days (first variant) and 7 days (second variant). After this period of time, from the moment of infection,  it proceeds to infect all usb drives attached to the computer using the classical autorun.inf technique.

       After 40 days from the infection (first variant) and 20 days (second variant) the malware goes and overwrites the MBR (master boot record) with garbage rendering the computer un-bootable.