Facebook does a lot of creepy things, like recommending that someone befriend their father’s mistress or connecting a couple with their anonymous sperm donor from years before. But how does Facebook tease out such obscure connections? Gizmodo investigated and traced Facebook’s behavior back to what’s known as “shadow contact information” — a secret database that Facebook keeps to track everyone you might know. It collects much of this information from other users who share their address books with Facebook, so if two otherwise unrelated people both have your phone number, the company can then connect them. Alas, there’s nothing you can do about this.