Genxlm

Description

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Just a simple script to generate JScript code for calling Win32 API functions using XLM/Excel 4.0 macros via Excel.Application COM object and "ExecuteExcel4Macro" method.

The script will generate a simple payload for performing a very basic shellcode injection by calling VirtualAlloc -> WriteProcessMemory -> CreateThread (just a poc, better options can be considered.)

Usage

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-o string output payload filename<br> -sh string Shellcode file path, ex: go run genXLM.go -sh shellcode.bin<br> -wsh string payload template js/hta, ex: go run genXLM.go -sh shellcode.bin -wsh js<br>

Detection:

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Currently not detected on VT;

• (0/56) VT https://www.virustotal.com/gui/file/f5a67b22f0362403b851664b6edd25928383d7f68099b61612e580b94734fe7a/detection

• XLM macros are not being covered by AMSI scans

• Instantiating Excel.Application COM objects from JS/VBS and calling ExecuteExcel4Macro is not flagged by WinDefender/AMSI

Details:

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Generate a simple JS using go run genXLM.go -sh shellcode.bin -wsh js and have a look at the generated js code "self-descriptive".

Check calc.hta, calc.js for examples. shellcode was generated using msfvenom.

References:

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• https://outflank.nl/blog/2018/10/06/old-school-evil-excel-4-0-macros-xlm/

Disclaimer:

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Use it for authorized red teaming and/or nonprofit educational purposes only. Any misuse of this script will not be the responsibility of the author. Use it at your own networks and/or with the network owner's permission.