Facebook Tracks Internet Users, Builds Secret Files

... files on the Internet activity of literally billions of Internet users. Website publishers use a variety of methods to track users' activity on their sites. Most of these fall into the category of placing cookies on the user's computer and are — at least to some degree — disclosed by the website's privacy policy.
From http://ift.tt/2oJAAci

... files on the Internet activity of literally billions of Internet users. Website publishers use a variety of methods to track users' activity on their sites. Most of these fall into the category of placing cookies on the user's computer and are — at least to some degree — disclosed by the website's privacy policy.