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This article introduces the relevant knowledge of "the method and specific process of removing private data in files under the Linux system". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

A typical data file is usually associated with "metadata", which contains the description of the file and is represented as a collection of attributes-values. Metadata generally includes the name of the creator, the tool that generated the file, the time when the file was created / modified, the location where it was created, the editing history, and so on. Several popular metadata standards are EXIF (pictures), RDF (web resources) and DOI (digital documents).

Although metadata has its advantages in the field of data management, it can actually endanger your privacy. The EXIF format data in the camera image will reveal identifiable personal information, such as the camera model, the GPS coordinates related to shooting and the user's preferred photo editing software. The metadata in documents and spreadsheets contains author / ownership information and related editing history. Not necessarily absolute, but metadata collection tools such as metagoofil are often used most as part of intrusion testing in the process of information collection.

For users who want to erase all personal metadata from shared data, there are ways to remove metadata from data files. You can use existing document or image editing software, usually with its own metadata editing function. In this tutorial, I will introduce a good, separate metadata cleanup tool with only one goal: anonymous all private metadata.

MAT (metadata Anonymous Toolbox) is a professional metadata cleaner written in Python. It is part of the Tor project and is standard with Trails, the Live version of the privacy-enhanced operating system.

Compared to tools such as exiftool, which can only write to a limited variety of file types, MAT supports the elimination of metadata from a wide variety of files: pictures (png, jpg), documents (odt, docx, pptx, xlsx, and pdf), archives (tar, tar.bz2), audio (mp3, ogg, flac), and so on.

Install MAT on Linux

On Debian-based systems (Ubuntu or Linux Mint), MAT has been packaged, so the installation is straightforward:

$sudo apt-get install mat

There is no pre-generated MAT package on Fedora, so you need to generate it from the source code. This is the step I took to generate MAT on Fedora (if not successful, see the bottom of the tutorial):

$sudo yum install python-devel intltool python-pdfrw perl-Image-ExifTool python-mutagen$ sudo pip install hachoir-core hachoir-parser$ wget https://mat.boum.org/files/mat-0.5.tar.xz$ tar xf mat-0.5.tar.xz$ cd mat-0.5$ python setup.py install

Using MAT-GUI Anonymous metadata

Once installed, you can use MAT from both the GUI and the command line. Enter this command to start the GUI of MAT:

$mat-gui

Try to clean up an instance document file (such as private.odt) that contains the following built-in metadata.

Click the "add" button to add files that need to be cleaned to MAT. Once the file is loaded, click the "OK" button to scan all hidden metadata information.

As long as the metadata is detected by MAT, the "State" status is marked as "Dirty". Double-click the file to view the detected metadata.

Click the Clean up button to clear the metadata in the file. MAT automatically clears all private metadata fields in the file.

The cleared state does not contain any privately identifiable traces:

Anonymous metadata from the command line

$mat-c.

As mentioned earlier, another way to invoke MAT is from the command line, which can be achieved using the mat command.

To check for any sensitive metadata, go to the directory where the file is located, and then run:

$mat-c.

This scans all files under the current directory and its subdirectories and reports their status (cleaned or not cleaned).

You can use the "- d" option to view the real metadata detected:

$mat-d

If no options are provided for the mat command, the default action removes the file's metadata. If you want to keep a backup of the original files during cleanup, use the "- b" option. The following command clears the metadata for all files and stores the original file as a "* .bak" file.

$mat-b.

To view the supported file types, run:

$mat-l

Troubleshooting

Currently I have encountered the following problems using the compiled version of MAT on Fedora. When I tried to clean up the metadata of the archive / document file (such as .gz, .odt, * .docx) in Fedora, MAT failed due to the following error. If you know how to solve this problem, please reply to me in the comments.

File "/ usr/lib64/python2.7/zipfile.py", line 305, in _ _ init__ raise ValueError ('ZIP does not support timestamps before 1980') ValueError: ZIP does not support timestamps before 1980

Summary

MAT is a simple but very useful tool to prevent inadvertent disclosure of private data from metadata. Please note that the contents of the file also need to be protected if necessary. What MAT can do is eliminate the metadata associated with the file, but it doesn't do anything about the file itself. In short, MAT is a lifeguard because it can handle most common metadata removals, but you shouldn't just count on it to keep your privacy.

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