
Ask HN: How has Facebook figured out my family doctor as a friend suggestion? - throwaway_374
I never use Facebook on my phone so you can hopefully rule out contact list networks - not that I ever had their personal mobile on my list - and location tracking because I haven&#x27;t attended my doctor&#x27;s surgery in years. We have zero friends in common. Other than my doctor actively looking me up on Facebook - highly unlikely - how on earth is this possible? I&#x27;m willing to accept friends of friends suggestions but this is beyond spooky.
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compsciphd
We've gone through this many times, its nothing nefarious.

1) doctor uploads his contacts (phone number/email addresses) to facebook and
sets his contact info

2) you upload your contacts and set your contact info

if there's one match between them, facebook believes (correctly) that there is
some sort of existing relationship between you. The fact that its professional
and not personal and you want facebook to just be personal doesn't change it.

In other cases facebook can see you are friends with many of them same people
and hence figures you might know each other.

~~~
yjftsjthsd-h
I think we could reasonably disagree about whether or not it's nefarious.
Siphoning everyone's contacts is iffy to start with.

~~~
jedimastert
It's not exactly without consent

~~~
uzoodoo
My old manager wanted me to install WhatsApp. WhatsApp wanted to access my
phone's address book so that it could upload all of my contact info to their
[Facebook's] servers. I denied it, and it refused to work. I didn't want to
share my contacts - I just wanted to communicate with a specific set of
people. The only workaround I could find is back up and delete all my contacts
before letting WhatsApp rummage through my address book.

I wouldn't say this practice is very "consensual".

~~~
paulcole
You wanted to use the app. The app makes the rules. Either use it or don't. I
don't see how they had a gun to your head.

~~~
uzoodoo
Sure, as Congressman Sensenbrenner said, “Well, you know... nobody’s got to
use the Internet”

[http://wapo.st/2nPh3JN](http://wapo.st/2nPh3JN)

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simonduponte
Factors that contribute to friend suggestions on FB:

1\. Facebook tracking pixels on websites (if you visit a website with the
pixel, you can be targeted in many different ways).

2\. Email. If you have sent or received an email to the doctor, and either of
you has associated that email to FB, you can be tracked.

3\. Searching on FB, you say its unlikely for him to look you up on FB, yet
theres always a chance that being a family doctor, he might have at some point
seen one of your family member's FB and stumbled upon a picture or post in
which you were tagged.

4\. Whatsapp Contacts. As you know, Whatsapp and FB are part of the same
company, hence have access to linked information. If you share certain
Whatsapp contacts, a connection can be inferred.

~~~
ams6110
I question point 2. Are you suggesting that Facebook reads my email? Have I
given them my email password? If not, how? (I ask, because I don't use
Facebook).

Sure, if we have each other's email addresses in our contact lists on
Facebook, I can see how the connection was made.

~~~
patcheudor
In this scenario you don't know if the doctor uploaded their contacts list to
FB. You further don't know if they are using a lousy e-mail app that sends
usage information to FB, perhaps as part of an advertising integration.

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badthingfactory
I had a surgical procedure done at the beginning of the year. I hadn't
explicitly shared this information at any point online or visited any websites
related to the surgery. A few days after visiting the hospital for some tests,
Google AdSense was showing me ads for surgeons at that specific hospital.

I'm not sure who I was most disappointed in. The hospital for purchasing the
ad, Google for tracking my hospital visits, or myself for trading privacy for
the convenience of services like Google Now.

~~~
pmiller2
And, to top it all off, those ads were utterly ineffective, since you'd
already had the procedure done!

Amazon and eBay have this same problem, wherein they show you things similar
to things you've already bought.

~~~
ceejayoz
> Amazon and eBay have this same problem, wherein they show you things similar
> to things you've already bought.

Which is especially silly when it's something you'd only buy once. "Oh, you
bought a table saw? Why not fifteen more?!"

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employee8000
The problem with all of these mobile apps is you just need ONE of your
contacts to upload your information, and then you're fucked. That's why I've
given up trying to hide my details because they already have it. The idea that
all 100% of my contacts respect my privacy is ridiculous unfortunately.

~~~
gvb
Definition: Your "Facebook ____" is the lowest ____ of any of your "friends"
that has a Facebook account.

Where ___ is any applicable attribute such as intelligence, privacy, etc.

Corollary 1: You will be surprised at who is included in the set of "friends"
that have a Facebook account.

Corollary 2: You will be surprised at how low the lowest ____ is for your
"friends."

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itake
I had something similar happen with an odd friend. I discovered that I shared
my address book with the messenger app. With gmail auto-adding contacts, you
might have been linked that way.

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lainon
[https://news.ycombinator.com/item?id=13259644](https://news.ycombinator.com/item?id=13259644)

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pmiller2
Besides every other suggestion here, couldn't it be that your doctor actually
_is_ a friend of a friend?

~~~
throwaway_374
Not possible as zero mutual friends, unless second degrees are considered
which based on all other suggestions is not the case and would naively scale
factorially (?).

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calvinbhai
Possibilities:

1) you have instagram or whatsapp and use them frequently

2) you use an app that has Facebook login, that has location access or just
has the SDK lying in app but not being used.

3) I don't know about what access react native/js frameworks have in terms of
device resources, but that "may be" an another source of info leak.

4) your contacts/friends uploaded a photo on one of these services where you
were there in the photo

5) if any of these apps have microphone access (when you record videos) it's
"possible" to do many surreptitious things.

All of the above, done by 1 or many of your friends/contacts on
Facebook/instagram/WhatsApp, FB identified you and correlated it somehow.

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tranv94
Facebook suggests a person I keep seeing on my commute that also works in the
same building as me (not same company). I always think the 0 mutual friend
recommendations are a bit weird/interesting

~~~
randomdata
To be fair, users who appear to travel in the same circles (even just an IP
address can reveal such correlation) seems like a fairly good choice for
making that kind of suggestion.

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unclesaamm
I think Facebook also connects people who appear at the same wireless access
points, so you could have received the suggestion once your phone connected to
the Internet at the doctor's office.

~~~
madamelic
Surprised this reply is this far down here.

The correct answer is that if you have the FB app installed, it tracks your
location. If you are in any place with another person with the FB app also
installed multiple times, it assumes you two know each other.

It is why therapists and other medical professionals should not have FB (or
any social network app, for that matter) installed on their phone (or,
alternatively, on while in the work place).

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code_duck
The most unusual friend suggestion I have received is a profile for the actor
Steve Martin. It had two mutual friends, and appeared 20 minutes after a
friend asked me "Have you ever listened to Steve Martin? The actor? He's also
a bluegrass musician" and played a couple of songs on Spotify.

Any ideas on how that came about? It's hard to believe it's anything other
than some app listening to audio.

~~~
nscalf
Do you log into spotify through facebook?

~~~
code_duck
Spotify was running on my friend's desktop. I have no FB apps installed other
than Instagram. I do not believe I had Spotify installed on my phone at the
time, though in the past, I have, and logged in through Facebook.

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madspindel
Something is indeed spooky with Facebook and their other products. I am friend
with a guy on Facebook and a person with the same name ended up as a
suggestion on Instagram - ok maybe not so spooky. But(!) this guy looked like
my friend except like ten years older. So I guess the combination of same name
+ looked like my friend (Facebook Face recognition) made Instagram suggest
this dude to me.

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DougN7
I have a similar, but even less connected case than a doctor: a contractor
that worked on my basement. No friends or clients in common that I know of.
I've never been to his office. Don't even know what town he lives in. I did
use FB on mobile for a short while, but probably didn't allow location info
(call me paranoid). I most definitely did not upload any contact list.

How can it be?

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jdavis703
How many other people in their recommendations list do you either not know at
all, or only know of them, but have never met? Whatever algorithms they use to
produce these recommendations (your social graph, IP addresses in common, etc)
will of course wind up surfacing a broad range of people, including some back
you actually know.

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sofaofthedamned
A Twitter acquaintance had a phone call from a website owner where he'd just
browsed their site, no relationship in any other way.

We _think_ they did a whois on his IP address which was at his company
address, which we all know is doable, but seeing companies proactively do this
is crazy.

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known
May be due to
[https://en.wikipedia.org/wiki/Six_degrees_of_separation](https://en.wikipedia.org/wiki/Six_degrees_of_separation)

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skdotdan
Either you have searched you doctor, or your doctor has searched you.

~~~
greyman
I believe this is the correct answer, it happened to me as well. I got friend
suggestion for my daughter speech therapist, and all our communication and
appointments were done only in paper form. But I searched her name on FB out
of curiosity. :-)

OP: Can you exclude the possibility that the doctor just searched your name on
FB? Why wouldnt he do that...?

~~~
maccard
> all our communication and appointments were done only in paper form

Just because your communication happened on paper doesn't mean that they
haven't stored your email address or phone number in some service digitally,
and that somehow that info has been shared (e.g. a phone with a facebook app
that uploads all contacts)

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maxsavin
Facebook tracks your location and the locations of others. If it sees that you
are around some people often, it might suggest you to be friends.

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thawab
the facebook/messenger app upload all contacts. if he has your phone number,
and your facebook account is registered with the same number, you will see a
friend suggestion. i don't use any of facebook's app on my phone and a few
time's i see a freind suggetion of people i just met in a week or less.

