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File metadata and controls

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🧹 Metadata Removal (EXIF & Co.)

Metadata is structured data about a file that is not directly visible in its content (like the pixels of an image or the text of a document), but reveals potentially sensitive information about the author, device, software used, and geographical location (GPS coordinates).

This module provides documentation and tools for file anonymization by removing this metadata using mat2 (Metadata Anonymisation Toolkit v2).

🛡️ Why Clean Metadata?

When you share a file (images, PDFs, audios, documents), you often inadvertently share:

  • GPS Coordinates: The exact location where a photo was taken.
  • Device Identifiers: The brand, model, and serial number of your camera or smartphone.
  • Software and History: Versions of image editing software, operating systems, local usernames, and file paths on your system.
  • Dates and Times: Exact file creation and modification timestamps.

🛠️ Recommended Tools

1. mat2 (Metadata Anonymisation Toolkit v2)

It is the standard anonymization tool recommended by PrivacyGuides and used in systems like Tails OS.

  • FOSS: Licensed under GPLv3, written in Python.
  • Operation Mode: Cleans metadata safely and destructively (by replacing the file or creating a clean copy).
  • Supported Formats: PNG, JPEG, TIFF, PDF, ODT, DOCX, PPTX, XLSX, MP3, FLAC, Torrent, among others.
  • Official Repository: https://0xacab.org/jvoisin/mat2

2. ExifTool

A highly powerful CLI tool for reading, writing, and editing metadata information. Used as an analysis complement.

📥 Installation

On Arch Linux (using Pacman)

sudo pacman -S mat2 perl-image-exiftool

On Debian/Ubuntu

sudo apt update
sudo apt install mat2 exiftool

📖 Usage Instructions

Analyze metadata without modifying the file

To check if a file contains suspicious/sensitive metadata using mat2:

mat2 --show file.jpg

Or using exiftool for a comprehensive analysis:

exiftool file.jpg

Clean metadata

By default, mat2 will create a copy of the file with the .cleaned extension (e.g., file.cleaned.jpg) free of metadata:

mat2 file.jpg

If you wish to clean the original file directly (overwriting it), use the -i or --inplace flag:

mat2 --inplace file.jpg

⚙️ Cleanup Methods

Option 1: Script Automation

We have provided the clean_metadata.sh script to automate metadata cleanup for individual files or entire folders recursively, verifying format compatibility beforehand to avoid terminal errors.

  1. Grant execution permissions:

    chmod +x clean_metadata.sh

  2. Run it by passing a file or directory as an argument:

    ./clean_metadata.sh /path/to/directory_or_file

Use the -i or --inplace flag before the path to overwrite the original files directly.

Option 2: Manual Recursive Cleanup (DIY)

If you prefer to skip the script and clean metadata recursively in a full directory using native terminal commands:

Standard cleanup (creates .cleaned copies)

find /path/to/directory -type f -exec mat2 {} +

Destructive cleanup (overwrites original files directly)

find /path/to/directory -type f -exec mat2 --inplace {} +

Note: Using find ... -exec mat2 directly will print warning messages for any unsupported file formats found. The automated script avoids this by validating format support for each file beforehand.