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Comment by paws | Hacker News Reader

> If you've ever given the service your number, you should consider your real identity linked to it.

I have a feeling it's worse than that. (I haven't rigorously perused the ToS, if I'm wrong please lmk.)

Let's say your friend John has an iPhone and saves your name and # in their contacts. One day John installs the Facebook app & opens it. John is not technical and when the app requests permissions he taps 'Allow'. At that point AFAICT there's nothing stopping Facebook from snagging your name & number and populating a ghost profile, or corroborating a real one.

In other words, if you've ever shared your phone number to someone who uses the Facebook app who doesn't dutifully and consistently reject permissions prompts, it's probably already too late.

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Your feeling is correct. It's been shown by researchers (incl. me) and confirmed by Facebook that they're doing that: https://gizmodo.com/facebook-is-giving-advertisers-access-to...

I’ve confirmed this same type of behavior in several of Google’s products as well, as part of an experiment a couple friends and I ran a several months back, using fake personas, to see how feasible it’d be for one to simply exist w/o creating a digital footprint (let’s just say that our overall conclusions left me feeling very sad).

Facebook frequently suggested my own mobile number to add it to my account when after I logged into the mobile webpage via phone (I never used any Facebook apps).

My only explanation for that was exactly that it had been farmed from a friends contact list.

Would rather not share the details here, but I know of one instance of a person having been found on Facebook via her phone number even though she never provided it - just one imprudent person who has your number associated with your real full name is enough for this to happen.

It’s like when you upload a photo with your friend (who doesn’t use Facebook) and it pops up ‘Did you want to tag [friend]?’

> ‘Did you want to tag [friend]?

You can tag someone that isn't on Facebook? I'm pretty sure the box use Facebook accounts...

Admittedly I didn't actually try it but I'm pretty sure said friend didn't have Facebook at the time (although they did get it, years later).

This is despicable.

You're exactly right. Add in the fact that Facebook can pose this as a puzzle to be solved, and attract a steady stream of sharp young people who can solve the puzzle without being bothered too much by the ethical consequences of solving the puzzle.

I've also definitely received "friend" suggestions for business contacts who I've had a phone number/email address stored in my phone.

There are no mutual friends or any other link it could make apart from linking my contact list with their number.

Facebook does indeed do that. One of the big reason of paying 22B for whatsapp is so that they could retrieve the entire friend graph of WhatsApp and use that to drive Facebook + Instagram MAUs.

The bigger the network, the more value a user gets, and the deeper the lock in.

It has been shown over and over again that both Facebook and Google will go to extreme lengths to know about their users’ lives and target them with precision ads. They are advertising companies foremost.

It would be interesting to see if there are ghost account numbers in the dataset. Depending on the country or region, would there be grounds for litigation if there were?

This is the entire business model of TrueCaller, and the reason they have a very accurate phone nbr lookup function

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