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Worm:ACAD/Kenilfe.A


First posted on 10 March 2011.
Source: SecurityHome

Aliases :

Worm:ACAD/Kenilfe.A is also known as Worm.Acad.Kenilfe.A, AutoCAD.Kenilfe, AL/Kenilfe.

Explanation :

A standalone malicious program which uses computer or network resources to make complete copies of itself. May include code or other malware to damage both the system and the network.

Additional DetailsThe worm is a malicious AutoCAD program that propagates via removable drives. It also attempts to download Visual Basic Scripts from remote servers, if certain conditions are met.

Installation

During installation, the malware creates the following registry entries:

  • HKEY_CURRENT_USER\Software\KenFiles\settings
    TMN = %Random Name% or "Temp"
    TMNL = %Random Name% or "TMNL"
    SHXN = %Random Name% or "isoshfr"
    CXBB = 102
    GXBZ = 103
    pth0 = %IP Address of updatebd.8800.org% (or "221223921023103" if cannot ping the host)
    pth3 = %Current Date%
    pth4 = %Current Date%
    pth5 = %Current Date%basepth = %User Support Folder%
    fontpth = %AutoCAD Fonts Folder%
It then creates copies of itself in the following locations:
  • %Folder of Current Drawing%\acad.fas
  • %User Support Folder%\acad.fas
  • %AutoCAD Fonts Folder%\%SHXN%.shx
Where %SHXN% is the same as the SHXN value found in the registry entry (above).

It also creates the following files:
  • %Windows Folder%\DivX.fin - possibly some sort of a infection marker
  • %Windows Folder%\system32\%TMN%.cmd - contains commands that will create copies of the malware (same as those mentioned earlier)
Where %TMN% is also the same as the TMN value found in the registry entry.

It enables the Windows Scripting Host by creating the following registry entry:
  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Script Host\Settings Enabled = 1

Then deletes the registry key:
  • "HKEY_CURRENT_USER\Software\FileKen\settings"
It also deletes the following files:
  • isohztxt.shx
  • acad.fas1
  • logo.gif
  • isomianyi.shx


Payload

Once installed, Kenilfe downloads and executes Visual Basic Scripts based on the following conditons:
  • http://www.cadgs.com/[...]/gxcx.[...] - if the 3rd octect of the IP address of updatebd.8800.org > 102
  • http://www.cadgs.com/[...]/gxmz.[...] - if the 4th octect of the IP address of updatebd.8800.org > 103
Example: if the IP address of updatebd.8800.org is 221.239.103.104, both Visual Basic Scripts will be downloaded and executed.

These conditions are specified in the CXBB and GXBZ registry, respectively.

Propagation

The malware enumerates all folders in all removable drives. If it finds the file acad.fas, it replaces the file with a copy of
  • %AutoCAD Fonts Folder%\isomianyi.shx.
Alternatively, if the folder contains a drawing (.dwg) file, it will create the file acad.fas (which is really a copy of isomianyi.shx).

It then creates a file named pagefile in the same drive location, to mark that it is done infected the drive.

During the enumeration process, the malware also renames the following files to append a "_bak" in their filenames:
  • acad.lsp
  • acad.sys
  • acad.vlx
  • acadapp.lsp
  • acadappp.lsp
  • acadapq.lsp
  • acadiso.lsp
  • acadsmu.fas
  • dwgrun.bat
  • isohztxt.shx
  • lcm.fas
  • winfas.ini

Last update 10 March 2011

 

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