Academic researchers said that the report showed that the company was breaking European law with its tracking policies. The law requires that users are told if their computers are receiving cookies except for specific circumstances.
Facebook’s tracking — which it does so that it can tailor advertising — involves putting cookies or small pieces of software on users’ computers, so that they can then be followed around the internet. Such technology is used by almost every website, but European law requires that users are told if they are being given cookies or being tracked. Companies don’t have to tell users if the cookies are required to connect to a service or if they are needed to give the user information that they have specifically requested.
But Facebook’s tracking policy allows it to track users if they have simply been to a page on the company’s domain, even if they weren’t logged in. That includes pages for brands or events, which users can see whether or not they have an account.