Why is Facebook recommending my friend to my other friends despite having nothing in common and having my list hidden

Question

I'm using Facebook only as a means of easy contact (mainly messenger). I have my privacy settings set as low as it was possible, with everything visible only to me. Basically everything that could be disabled from publishing, I did.

I lately saw that my good friend I met on the internet (and has completely no relations with any of my other friends! He's not even living in the same part of the country.) has appeared in the "recommended friends" of my friend from real life, despite me not really having any special contact with him over Facebook. He is only in my friends list, I'm not even messaging him or anything. Of course on the recommended list there was a note that there's one mutual friend, but didn't show who because I got my friends list hidden.

If he got my kinda private internet friend recommended (for some reason that I cannot even think of), it means that everyone from my friends can get him in recommended too. It kinda bothers me because I have disabled my friends list for a reason, I don't want others to see my friends AT ALL, and when they see that there's some single mysterious mutual friend, then they can easily assume it's me because there aren't many people like me who disable everything.

I could understand if there was more than one mutual friend, but it's only me, with everything hidden and it's a person that I'd rather not want floating around my real-life friends. They could just easily invite them and then they'd see them in my friend's list, because it shows mutual friends. I think that's kind of a privacy concern and there should be an option to actually NOT share some of your friends to everyone around you. I'm pretty sure there are hundreds of other friends that could be recommended, that actually have anything in common.

Is there any way I could prevent this from happening other than deleting them?

Answer 1

Facebook's various mobile apps (including Messenger) have been known or suspected of using the phone's contacts, call logs, and GPS location to suggest "people you may know." This can be creepy and troubling.

See Facebook’s ‘People You May Know’ feature can be really creepy. How does it work?

If you give Facebook your phone number even just for login verification, they've been known to use that to recommend you to people who've called you. That could be troubling if you're a psychiatrist. See Facebook to Stop Using Phone Numbers for Recommending Friends.

This page might help: How to Not Show Up in Suggested Friends on Facebook. Also Facebook Is Tracking Your Every Move on the Web; Here's How to Stop It.

Also consider deleting all Facebook made apps from your mobile devices.