XLMMacroDeobfuscator 0.1.3

XLMMacroDeobfuscator is an XLM Emulation engine written in Python 3, designed to analyze and deobfuscate malicious XLM macros, also known as Excel 4.0 macros, contained in MS Excel files (XLS, XLSM, and XLSB).

XLMMacroDeobfuscator

XLMMacroDeobfuscator can be used to decode obfuscated XLM macros (also known as Excel 4.0 macros). It utilizes an internal XLM emulator to interpret the macros, without fully performing the code.

It supports both xls, xlsm, and xlsb formats.

It uses xlrd2, pyxlsb2 and its own parser to extract cells and other information from xls, xlsb and xlsm files, respectively.

You can also find XLM grammar in xlm-macro-en.lark

Installing the emulator

1. Install using pip

pip install XLMMacroDeobfuscator

2. Installing the latest development

pip install -U https://github.com/DissectMalware/XLMMacroDeobfuscator/archive/master.zip

Running the emulator

To run the script

xlmdeobfuscator --file document.xlsm

Usage

usage: deobfuscator.py [-h] [-f FILE_PATH] [-n] [-x] [-2] [-s] [-d DAY]
                       [--output-formula-format OUTPUT_FORMULA_FORMAT]
                       [--no-indent] [--export-json FILE_PATH]

optional arguments:
  -h, --help            show this help message and exit
  -f FILE_PATH, --file FILE_PATH
                        The path of a XLSM file
  -n, --noninteractive  Disable interactive shell
  -x, --extract-only    Only extract cells without any emulation
  -2, --no-ms-excel     Do not use MS Excel to process XLS files
  -s, --start-with-shell
                        Open an XLM shell before interpreting the macros in
                        the input
  -d DAY, --day DAY     Specify the day of month
  --output-formula-format OUTPUT_FORMULA_FORMAT
                        Specify the format for output formulas ([[CELL_ADDR]],
                        [[INT-FORMULA]], and [[STATUS]]
  --no-indent           Do not show indent before formulas
  --export-json FILE_PATH
                        Export the output to JSON

Read requirements.txt to get the list of python libraries that XLMMacroDeobfuscator is dependent on.

You can run XLMMacroDeobfuscator on any OS to extract and deobfuscate macros in xls, xlsm, and xlsb files. No need to install MS Excel.

Note: if you want to use MS Excel (on Windows), you need to install pywin32 library. if you do not want to use MS Excel, use --no-ms-excel. Otherwise, xlmdeobfuscator, first, attempts to load xls files with MS Excel, if it fails it uses xlrd2.

* This code is still heavily under development. Expect to see radical changes in the code.