Get ready for a data overload: Metadata is the data that describes all of the other data in a file. Still with us? Good, because there’s more!
Metadata is very useful as it reduces the amount of information needed to process a file and can make especially large files easier to manage.
The Two Main Types of Metadata
Structural metadata is information relating to how data is stored.
Often structural metadata can be observed and calculated just from looking at the file. Let’s imagine the file we are looking at as a book: the structural metadata would include whether the cover is hard or soft, the shape of the book, and its weight and dimensions.
The structural metadata of a phone conversation would include the length and time of the conversation.
In the case of a digital image, the metadata would include the size and the file type.
Descriptive metadata is additional information that helps humans and computers learn the contents of books and files.
A book’s descriptive metadata will include the title, author, printing data, edition, and possibly even a short summary in the back. The ISBN number is also part of this descriptive metadata.
A phone conversation would also have a lot of descriptive metadata attached to it, for example, who made the call, who the call was to, and where the call was made from.
For an image, the descriptive metadata can be extremely vast. It can include the manufacturer of the camera, any editing software used, lens aperture time, exposure time, orientation, color space, brightness, the owner of the camera, and even the GPS location of the image.
John McAfee Arrested after Metadata Revealed His ‘Safe Spot’
Metadata can often reveal more about a file than the actual data. John McAfee is famous for the antivirus company named after him, and for being the current presidential candidate for the Libertarian Party — but he still had to witness the brutal effects of ignoring your Metadata the hard way…
Back in 2012, McAfee was living in Belize when his neighbor was found dead of a gun wound to his head. For some reason, McAfee was scared he might become a suspect in the investigation. Possibly high on bath salts and deeply paranoid, McAfee chose to flee the friendly inquiries of the police and hide in the jungle instead.
McAfee did keep in touch with a few journalists from Wired and Vice, though. Vice’s editor-in-chief, Rocco Castoro and Wired photographer, Robert King followed McAfee around for a few days, posting online updates like this one:
The pictures, taken with an iPhone 4S, recorded the trio’s movement through the Belize jungle. Their current location was attached to every picture and what they didn’t realize was that this data did not simply disappear after the image was uploaded. While it was invisible to the human eye, it still remained part of the metadata of the image files.
As the metadata contained the GPS coordinates of every image that was taken, the authorities were led straight to McAfee.
Anyone can see the metadata associated with McAfee’s pics, by opening the image files with Julien Voisin’s Metadata Anonymisation Toolkit:
Entering the coordinates from the picture into Google Maps, we can see that the trio were at a luxurious resort called the Mar Marine Yacht Club in Guatemala, not far from the Belize border.
Some services do remove the metadata from your files automatically when you upload them, but it is hard to predict which services do that, and which metadata they will remove.
Software That Will Delete the Metadata from Your Files
Depending on your platform, several tools exist that allow you to inspect and remove metadata from your files.
Mac OS X: ImageOptim
Windows: Microsoft Office Document Inspector
Removing Metadata Protects Your Anonymity Online
We very much recommend you check each image before you upload it, especially in situations where you want to conceal your identity. Better not to rely on software to do this automatically!