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Ask HN: How has Facebook figured out my family doctor as a friend suggestion?

• thawab 9y ago
  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.
• lainon 9y ago
  https://news.ycombinator.com/item?id=13259644 https://news.ycombinator.com/item?id=13259644
• skdotdan 9y ago
  Either you have searched you doctor, or your doctor has searched you.
  • greyman 9y ago
    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 9y ago
      > 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)
    • always_good 9y ago
      A girl I talked to on Tinder a few years ago popped up on my People You May Know list. I befriended her and met up with her recently. I brought it up to her, we wondered how it happened, and she admitted that she'd searched for my profile a week before. I'd say this aspect of the system is a good feature. If you're searching for someone, it's nice to give them an opportunity to "independently" reach out to you.
• itake 9y ago
  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.
• badthingfactory 9y ago
  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 9y ago
    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 9y ago
      > 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?!"
• jdavis703 9y ago
  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.
• simonduponte 9y ago
  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.
  • patcheudor 9y ago
    I'm glad you covered the bi-directional aspects of the association. A number of years ago FB had a vulnerability I discovered whereby it was possible to register an account with an e-mail you don't own. Obviously it wouldn't be possible to then verify the account if the owner of the e-mail targeted failed to click on the verify link. To get around this, upon first authenticating with the account after registration it was possible to change the e-mail address to one you own then send a very request. After verification, it was then possible to change it back to the original e-mail at which point it was verified. In testing with a few people who never even had FB accounts and who I clearly did not import any contacts, etc., was that they fairly immediately received friend suggestions and even requests from people they knew. This was also despite the fact they'd never used the computer or even IP address used in the registration of the account. At the time it helped me prove a point that not participating in social media could be a security problem & to always take social media verification seriously. Obviously FB has since fixed that vector.
    • caseysoftware 9y ago
      This was easy to do as late as 2010. I haven't tried it recently but it was a common attack for quite a while: https://caseysoftware.com/blog/social-media-for-social-evil-part-i-impersonation https://caseysoftware.com/blog/social-media-for-social-evil-...
• employee8000 9y ago
  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 9y ago
    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."
• compsciphd 9y ago
  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 9y ago
    I think we could reasonably disagree about whether or not it's nefarious. Siphoning everyone's contacts is iffy to start with.
    • jedimastert 9y ago
      It's not exactly without consent
      • mtgx 9y ago
        It pretty much was the entirety of the Facebook app's life. And it only somewhat changed when Google introduced permissions where the user actually has to opt-in (post app install).
      • naner 9y ago
        Everyone in the contact list didn't provide consent. Facebook better understands the privacy implications here more than individual users so I don't see anything wrong with placing most of the blame on Facebook.
      • detaro 9y ago
        Going to a doctor implies consent to have your contact data shared with Facebook?
      • uzoodoo 9y ago
        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".
• pmiller2 9y ago
  Besides every other suggestion here, couldn't it be that your doctor actually is a friend of a friend?
  • throwaway_374 9y ago
    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 (?).
• tranv94 9y ago
  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 9y ago
    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.
• known 9y ago
  May be due to https://en.wikipedia.org/wiki/Six_degrees_of_separation https://en.wikipedia.org/wiki/Six_degrees_of_separation
• code_duck 9y ago
  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 9y ago
    Do you log into spotify through facebook?
    • code_duck 9y ago
      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.
• unclesaamm 9y ago
  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 9y ago
    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).
• maxsavin 9y ago
  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.
• calvinbhai 9y ago
  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.
• madspindel 9y ago
  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.
• sofaofthedamned 9y ago
  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.
• DougN7 9y ago
  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?