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Comment by Harkins | Hacker News Reader

They still have your face from scanning your friends' photos and contacts. Combine datestamp, location, messages, and posts over years and Facebook knows who was together for a photo whether or not you've uploaded any or been tagged. Facebook knows the face of everyone who is on Facebook or who knows a few people who are.

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I can pull a fingerprint off the subway stair rails but that doesn't mean I can identify who it is. We anonymously reveal ourselves everyday but the danger comes from confirming which data is ours. The goal is to make it difficult not impossible.

They don't need you to confirm it. This isn't a criminal case. They just need to be reasonably confident. Your face is in a picture with four other people. They can see that phones belonging to four people, who regularly chat with each other, were all at the same location at the time the photo was taken. They are now reasonably confident that your face is one of those four. Do that five or six times and their robots will know your face. Whether you confirm it or not doesn't really matter.

  They can see that phones belonging to four people, who regularly chat with each other, were all at the same location at the time the photo was taken.

How would they "see" your phone without the facebook app installed?

They buy/rent that data from google or any of a thousand other companies that might have access to your phone's location.

Thing is: Grabbing fingerprints from the subway doesn't scale. Machine learning does.

No, not really. There are not many of photos of me on the web and any that are were taken from a distance and too low res to id me.

I've been stingy about that for a long time. FB doesn't have my phone number and I disabled the email address I used to sign up. I delete all my cookies often and use different browsers and turn off and reset my modem to get a new IP address.

I have no apps on my phone, don't use iCloud, and don't use the native "Contacts" app, I made my own for that.

I know I'm still being tracked, but not as much as most and I don't think FB could ID me right now with photos they have.

> FB doesn't have my phone number

If anyone who has you in their contact list uses Facebook, I can pretty much guarantee they have your number.

Yeah this is the real rub; even if you yourself do not give Facebook information, it's been proven that they collect profiles on you. Anyone who has messaged you, has you in their contacts, sent you invites, added you to groups, all this gets added to a hidden profile. You are being tracked whether you gave out info or not.

>don't use the native "Contacts" app, I made my own for that.

That's a good idea. You could then grant other apps permission to see your contacts, but have the app optionally return fake or empty data.

This. Fake data should always be returned, unless explicit permission is granted for real data.

I doubt iOS lets a custom contacts app respond to a request from another app for contacts though. It'll presumably respond empty data (since they have no contacts in the native app), but with no option to give it the actual contacts if you wanted to.

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