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Date discovered:21/06/2011
In the wild:Yes
Reported Infections:Low to medium
Distribution Potential:Low
Damage Potential:Low to medium
Static file:Yes
File size:47.104 Bytes
MD5 checksum:d54cbd070378e655f398979ac7caca5c
IVDF version:

 General Aliases:
   •  Kaspersky: Backdoor.Win32.VB.nmc
   •  Bitdefender: Backdoor.Generic.644760
   •  GData: Backdoor.Generic.644760

Platforms / OS:
   • Windows 2000
   • Windows XP
   • Windows 2003

Side effects:
   • Drops malicious files
   • Registry modification
   • Makes use of software vulnerability
      •  CVE-2007-1204
      •  MS07-019

 Files It copies itself to the following location:
   • %TEMPDIR%\736si.exe

It overwrites a file.

It deletes the initially executed copy of itself.

It deletes the following file:
   • %TEMPDIR%\mdinstall.inf

The following files are created:

%TEMPDIR%\mdinstall.inf This is a non malicious text file with the following content:
   • %code that runs malware%


It tries to execute the following files:

– Filename:
   • net.exe stop "Security Center"

– Filename:
   • %TEMPDIR%\736si.exe -d3E2D806A4C8B24FB16E73F18783CA1A4DB4E81F14022DC15B1DDA7D115C3D2BAB4C8312CFD81BDE34430CC638BB53810A0638C640FA4A5F9B78E760A0A75CCBE3A7341EEE5EDC428F6B75D1AE219171D6156357952E3212173C1B1D908FCB93FB7E000120F1113A3A16794C3985BE5B0229F6E5D366D

– Filename:
   • "%SYSDIR%\grpconv.exe" -o

– Filename:
   • sc config wscsvc start= DISABLED

– Filename:
   • net.exe stop "Windows Firewall/Internet Connection Sharing (ICS)"

– Filename:
   • sc config SharedAccess start= DISABLED

– Filename:
   • %TEMPDIR%\736si.exe

– Filename:
   • net1 stop "Security Center"

– Filename:
   • net1 stop "Windows Firewall/Internet Connection Sharing (ICS)"

– Filename:
   • Rundll32.exe setupapi,InstallHinfSection DefaultInstall 128 %TEMPDIR%\mdinstall.inf

– Filename:
   • cmd /c %TEMPDIR%\ogvoirym.bat

 Registry The following registry key is added in order to run the process after reboot:

– [HKLM\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\
   • "j44h"="%TEMPDIR%\736si.exe"

The following registry key is added:

– [HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce]
   • "GrpConv"=""

The following registry keys are changed:

– [HKCU\Software\Microsoft\Windows\CurrentVersion\GrpConv]
   New value:
   • "Log"="Uninit Application."

– [HKLM\SOFTWARE\Classes\MSProgramGroup\Shell\Open\Command]
   New value:
   • "@"="%SYSDIR%\grpconv.exe %1"

– [HKLM\SOFTWARE\Classes\MSProgramGroup]
   New value:
   • "@"="Microsoft Program Group"

– [HKLM\SOFTWARE\Classes\.grp]
   New value:
   • "@"="MSProgramGroup"

 Hosts The host file is modified as explained:

– In this case existing entries are deleted.

– Access to the following domain is redirected to another destination:
   • localhost

 Backdoor Contact server:
The following:
   • http://w.nucleardiscover.com:888/**********?c=%character string%&v=%number%&t=%character string%

 Miscellaneous Mutex:
It creates the following Mutexes:
   • 736si.exej44h
   • 736si.exej44hdmode

 File details Programming language:
The malware program was written in Visual Basic.

Runtime packer:
In order to aggravate detection and reduce size of the file it is packed with a runtime packer.

Descripción insertada por Petre Galan el jueves, 14 de julio de 2011
Descripción actualizada por Petre Galan el jueves, 14 de julio de 2011

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