With the advance of technologies and the development of connected devices, the concern about data privacy is raising. The Cambridge analytica scandal in 2018 and Edward Snowden's revalations in 2013 showed how the users data can be used, and that users barely have control over their own data. Once you have sent a picture of you at the beach to your friends, or shared your status on facebook, who knows where this information is going to be stored, and who can access and use it. Even though data privacy is becoming an important topic regarding privacy, metadata is not less important.
What are metadata?
The "meta" word comes from the greek (μετά) and means beyond. Metadata would, thus, be the data beyond the data. Sometimes, it can also be referred to as the data about the data. So, in case this little explanation is not clear, metadata are the data giving specification on the data themselves. For example, if you take a picture with your smartphone, the metadata could contain:
- time at which the picture was taken;
- focal length of the camera;
- which camera/smartphone was used (brand and model);
- resolution of the pictures;
- GPS coordinate (eventually);
- and many more...
You can easily check that by opening the gallery on your smartphone, and look at the "info" of the pictures.
To summarize, when you send a picture, you also send all the information regarding your camera (or smartphone), your location and the time at which the picture was taken.
Metadata... and so what?
So now, you might be wondering: "O.K., Jimmy, I send info about my camera, and so what?"
Well, if you are concerned about data privacy, sharing all your metadata should be also of your concern. By sharing all this information, people could easily track your phone model (that one is easy), but also your position, and, since the timestamp of the pictures might also be available, your whole journey can be inferred. It can also be easy to find out what your habits are. Maybe are you everyday at 10 am at your favorite bakery, meanwhile, your house is not watched. All this information comes not only from your camera, but also, for example, from your GPS, when that one is all the time turned on and most applications have access to it, without you not necessarily noticing.
Furthermore, some people in their job might also need to have a full control on their metadata and be aware of what they share. For example lawyers and journalist might have to protect the anonymity of their sources. You can also think about medical secret.
A good example on how the metadata can be explicitly used to track down someone's habit can be seen in the documentary "Nothing to hide". A whole profile can be made such as guessing your work, political ideas and much more. Also, the story of how FBI Used Metadata to Catch CabinCr3w Hacker after posting a picture of his girlfriend.
So what can you do?
We now live in a world in which sending documents via email, smartphone, cloud, etc is almost mandatory. So what if you want to preserve this precious meta-information? Well, the solution depends on the kind of documents involved. Several programs used to create document also implement a solution to remove the metadata. If you work in a company, and you can afford to spend some money, you can check MetaDact. They provide a solution for several sort of document, plus an analysis of risk and clean the data send by email from your smartphone. For a 'free' alternative, you can check several solutions depending on your needs. For example, you can use the document inspector for your Microsoft Office files, and for pdf files you can use Adobe Acrobat or PDFelement Pro. For pictures, you can directly use Lightroom, Photoshop or GIMP. These 3 applications provide a direct way to edit the metadata from your pictures. On Android, you can look for the Scrambled Exif application, also available on several Android markets. This list of applications is non-exhaustive and you can search for a tool that can fit better your needs.
One general solution, that I found quite interesting, is exiftool, which is a multi-platform tool that can take care of several types of documents. You might need to investigate a bit the documentation in order to get it modify your metadata as you wish, but I found it quite powerful. Sometimes, it would event give me some information for pictures that were not available in GIMP. Below is the output from exiftool on a picture file.
File Modification Date/Time : 2016:10:24 16:40:12+04:00
File Access Date/Time : 2016:10:24 16:40:17+04:00
File Inode Change Date/Time : 2016:10:24 16:40:12+04:00
File Permissions : rw-r--r--
File Type : JPEG
File Type Extension : jpg
MIME Type : image/jpeg
JFIF Version : 1.01
Resolution Unit : inches
X Resolution : 300
Y Resolution : 300
Exif Byte Order : Big-endian (Motorola, MM)
Make : NIKON CORPORATION
Camera Model Name : NIKON D5200
Exposure Time : 1/1600
F Number : 7.1
ISO : 400, 0
Date/Time Original : 2016:10:24 10:27:05
Flash : Unknown (24 0)
Focal Length : 105.0 mm
Image Width : 960
Image Height : 640
Encoding Process : Baseline DCT, Huffman coding
Bits Per Sample : 8
Color Components : 3
Y Cb Cr Sub Sampling : YCbCr4:2:0 (2 2)
Aperture : 7.1
Image Size : 960x640
Megapixels : 0.614
Shutter Speed : 1/1600
Focal Length : 105.0 mm
Light Value : 14.3
You can see the level of details that are contained withing the file, and this is far from being the most precise set of metadata you can get. From this file, we can get the time at which the picture was taken and the model of the camera. Also, the speed and the focal length of the camera settings are available. Sometime, the mode of the camera can also be known. This camera does not have a GPS, but what if it had one?
All these information at first might seem irrelevant, but they can tell much more about you and about your life than you can think of. That is why, it is important to keep all this information under control and be aware of what you are sharing with the rest of the world.