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3 years ago
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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-lark.template
Installing the emulator
Install using pippip install -U https://github.com/DissectMalware/pyxlsb2/archive/master.zip
pip install -U https://github.com/DissectMalware/XLMMacroDeobfuscator/archive/master.zip
Running the emulator
To deobfuscate macros in Excel documents:
To only get the deobfuscated macros and without any indentation:
To export the output in JSON format
To see a sample JSON output, please check this link out.
To use a config file
default.config file must be a valid json file, such as:
"no-indent": true,
"output-formula-format": "[[CELL-ADDR]] [[INT-FORMULA]]",
"non-interactive": true,
"output-level": 1
}
Command Line
emulation after N seconds (0: not interruption N>0: stop emulation after N seconds) ">
_ _______
|\ /|( \ ( )
( \ / )| ( | () () |
\ (_) / | | | || || |
) _ ( | | | |(_)| |
/ ( ) \ | | | | | |
( / \ )| (____/\| ) ( |
|/ \|(_______/|/ \|
______ _______ _______ ______ _______ _______ _______ _______ _________ _______ _______
( __ \ ( ____ \( ___ )( ___ \ ( ____ \|\ /|( ____ \( ____ \( ___ )\__ __/( ___ )( ____ )
| ( \ )| ( \/| ( ) || ( ) )| ( \/| ) ( || ( \/| ( \/| ( ) | ) ( | ( ) || ( )|
| | ) || (__ | | | || (__/ / | (__ | | | || (_____ | | | (___) | | | | | | || (____)|
| | | || __) | | | || __ ( | __) | | | |(_____ )| | | ___ | | | | | | || __)
| | ) || ( | | | || ( \ \ | ( | | | | ) || | | ( ) | | | | | | || (\ (
| (__/ )| (____/\| (___) || )___) )| ) | (___) |/\____) || (____/\| ) ( | | | | (___) || ) \ \__
(______/ (_______/(_______)|/ \___/ |/ (_______)\_______)(_______/|/ \| )_( (_______)|/ \__/
XLMMacroDeobfuscator(v0.1.7) - https://github.com/DissectMalware/XLMMacroDeobfuscator
usage: deobfuscator.py [-h] [-c FILE_PATH] [-f FILE_PATH] [-n] [-x] [-2]
[--with-ms-excel] [-s] [-d DAY]
[--output-formula-format OUTPUT_FORMULA_FORMAT]
[--no-indent] [--export-json FILE_PATH]
[--start-point CELL_ADDR] [-p PASSWORD]
[-o OUTPUT_LEVEL]
optional arguments:
-h, --help show this help message and exit
-c FILE_PATH, --config_file FILE_PATH
Specify a config file (must be a valid JSON file)
-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 [Deprecated] Do not use MS Excel to process XLS files
--with-ms-excel 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
--start-point CELL_ADDR
Start interpretation from a specific cell address
-p PASSWORD, --password PASSWORD
Password to decrypt t he protected document
-o OUTPUT_LEVEL, --output-level OUTPUT_LEVEL
Set the level of details to be shown (0:all commands,
1: commands no jump 2:important commands 3:strings in
important commands).
--timeout N stop emulation after N seconds (0: not interruption
N>0: stop emulation after N seconds)
Library
The following example shows how XLMMacroDeobfuscator can be used in a python project to deobfuscate XLM macros:
result = process_file(file='path/to/an/excel/file',
noninteractive= True,
noindent= True,
output_formula_format='[[CELL-ADDR]], [[INT-FORMULA]]',
return_deobfuscated= True,
timeout= 30)
for record in result:
print(record)
Requirements
Please read requirements.txt to get the list of python libraries that XLMMacroDeobfuscator is dependent on.
xlmdeobfuscator can be executed on any OS to extract and deobfuscate macros in xls, xlsm, and xlsb files. You do not need to install MS Excel.
Note: if you want to use MS Excel (on Windows), you need to install pywin32 library and use --with-ms-excel switch. If --with-ms-excel is used, xlmdeobfuscator, first, attempts to load xls files with MS Excel, if it fails it uses xlrd2 library.
Project Using XLMMacroDeofuscator
XLMMacroDeofuscator is adopted in the following projects:
CAPE Sandbox FAME REMNUX IntelOwl Assemblyline 4 by Canadian Centre for Cyber SecurityPlease contact me if you incorporated XLMMacroDeofuscator in your project.
How to Contribute
If you found a bug or would like to suggest an improvement, please create a new issue on the issues page.
Feel free to contribute to the project forking the project and submitting a pull request.
You can reach me (@DissectMlaware) on Twitter via a direct message.
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