We all use various platforms like Facebook, Twitter, Instagram, etc to share our thoughts and behavior. Most of them were shared as media files including images, videos, and PDFs. Every file we share will give some information about us we don’t intend to share which we call meta-data.
What is meta-data?
Meta-data is data about data. For instance, when we capture a photo using a camera it contains certain information about the camera model, exact date-time of the click and even the geo-location and shutter speed. These details are not visible to human eyes rather they are embedded in the file which can be read pragmatically.
Does it matter ?
“I don’t do phonographic images, I don’t have anything to hide so why I should bother?” As security educators, this is a common misconception we hear regulatory.
Maybe you don’t have anything to hide (yet) still the content you are sharing will be uploaded to servers that may have downloaded by attackers then searched through their meta-data to create profiles of its users.
How to remove meta-data easily ?
In this post, we are using a free and open-source software tool developed by Phil Harvey. Written in Perl, ExifTool is a platform-independent software that you can run in Windows, Mac, and Linux based operating systems without a hassle.
Installing & Run ExifTool
The ExifTool does not need to be installed to run. Just download and extract on Mac/Linux, and for Windows EXE version is available. [https://exiftool.org/install.html]
Common ExifTool commands
View all meta-data from a given image:
The below image shows an extract from the result of an image I took on my mobile phone. (There were 30+ meta-data tags)
Removing all meta-data from a given image:
exiftool -all= IMAGE.jpg
After running exiftool to extract meta-data, it ended up with 18 meta-data key-value pairs which are mandatory for any image file.
Observe the above image after extracting meta-data the image will only have the mandatory meta-data that can not be used to relate to the original owner.
Adding new tags to existing files.
Adding new tags to existing files is not straightforward.
To add a new tag or to update an existing tag, you need to use the relevant prefix based on the group that relates to the file.
To find the group name based on the file type refer to the below table:
In my example, I’m going to use a JPEG file type so I need to find an existing tag listed under the JPEG Tag category.
exiftool -exif:UserComment=cybermemos.com IMAGE.jpg
Below are the command and the output when adding the UserComment tag into my JPG file. (Remember the tags are case insensitive)
It is not always bad to add meta-data to our files. Below are some cases that we can use meta-data in a useful manner.
- Add copyright information to your work.
- Adding keywords to be read by ATS systems (Read more about ATS systems)
- Basic level of steganography (Hiding information like password hints inside meta-data)
- Use meta-data to organize your files (You can write a program to read meta-data from files and organize them based on date)
Any other thing you can think of? Let us know in the comments section.