Remove Metadata from Files Before Sharing on Tor

Images: JPEG and PNG files can contain EXIF data including camera make and model, serial number, GPS coordinates where the photo was taken, date and time, and even a thumbnail of the original image (which may show content you cropped out). A single photo with GPS coordinates can reveal your home or workplace.

Documents: PDF files often contain the author name (pulled from your OS user account), software version, creation and modification timestamps, and sometimes the full edit history. Microsoft Office documents can contain author names, organization names, revision history, comments, and hidden text. LibreOffice documents carry similar metadata.

Audio and Video: MP3 files contain ID3 tags with artist, album, and software information. Video files can include camera metadata, GPS data, and software information. Even screen recordings can leak your screen resolution, OS version, and timezone through embedded metadata.

MAT2 (Metadata Anonymisation Toolkit 2) is the recommended tool for metadata removal on Linux. It is pre-installed on Tails and available in most distributions: sudo apt install mat2. MAT2 supports images (JPEG, PNG, TIFF), documents (PDF, DOCX, ODT), audio (MP3, OGG, FLAC), video, and archive files.

Basic usage: mat2 filename.jpg creates a cleaned copy with the suffix .cleaned. To clean in place: mat2 --inplace filename.jpg. To process an entire directory: mat2 *.jpg. To check what metadata exists before cleaning: mat2 --show filename.jpg.

MAT2 is thorough but not infallible. It removes known metadata fields but cannot detect steganographic watermarks or statistical fingerprinting embedded in the file's content itself. For maximum safety, consider converting files to a simple format (e.g., re-encoding an image as PNG, or printing a PDF to a new PDF) in addition to running MAT2.

ExifTool is a powerful command-line utility for viewing and removing metadata from image files. Remove all metadata: exiftool -all= filename.jpg. View all metadata: exiftool filename.jpg. ExifTool supports over 400 file formats and provides more granular control than MAT2 for image-specific metadata.

For PDF files, qpdf --linearize input.pdf output.pdf can strip some metadata. For complete PDF cleaning, use MAT2 or print the PDF to a new file through a virtual printer. The pdftk tool can also remove metadata: pdftk input.pdf dump_data | sed '/^Info/d' | pdftk input.pdf update_info - output clean.pdf.

For the most paranoid approach, open files in a viewer inside a virtual machine (such as Whonix or Tails), take screenshots, and share the screenshots instead of the original files. This eliminates all metadata and all steganographic watermarks, at the cost of quality and editability.

For organizations that regularly process and share sensitive files, AnubizHost provides offshore VPS hosting where you can deploy automated metadata removal pipelines. Run MAT2, ExifTool, and custom cleaning scripts on a dedicated server accessible only as a Tor hidden service.

Build a secure document processing workflow: upload files through OnionShare, automatically strip metadata with MAT2, and publish cleaned files through your .onion site. Our servers in Iceland, Romania, and Finland provide the offshore jurisdiction and privacy protection your workflow needs.

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