Are you responding to the connotation of, say, Cold War intelligence with the use of ‘file’? For me it’s pretty trivial that Facebook can pull up information per IP, correlated IP (via accounts, usage, magic pixel) and try to work from there. I doubt it’s legal under GDPR to store all that data, but it never sees light and they could argue that they need it for compliance with things like law enforcement and keeping their own platform usable regarding bots and misuse. (Not giving my opinion regarding this tracking by FB here.)
Yeah I think it's in their interest to identify internet users for targeted ads, so they have what would amount to Stasi-like files on people. Correlating all the info they have to try and determine an internet users true identity, and they sure have a lot of information.
