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How Facebook's Safety Check Works
- Amorymeltzer 11y agoA longer, more involved article from late September has a bit more information: http://highscalability.com/blog/2015/9/28/how-facebook-tells-your-friends-youre-safe-in-a-disaster-in.html http://highscalability.com/blog/2015/9/28/how-facebook-tells... >If a friend is in the same area then a push notification is sent asking if they are OK. One thing that I'd like to understand is how "area" is defined. The limiting factor is, of course, finding out something has happened, but someone at Facebook has to draw a border that encompasses everyone at risk but minimizes those out of harm's way. An earthquake is almost easier - there's (relatively) rapid data on the epicenter and size - but in an event and place like Paris, there have got to be some hard calls made in real time. Who are the people and teams involved there, and how do they make those decisions? I'd love to see that.
- chipperyman573 11y agoThey probably are very generous - I'd imagine the entire country was defined as the "area". The system doesn't work very well if there's false negatives and people don't see it, and if someone sees it but shouldn't all they have to do is hit that they're OK.
- xxbondsxx 11y agoNot quite @chipperyman573. A few points to make here: -- Since we only have city-level location for most users, declaring the area isn't as hard as drawing on a map. We usually just select a number of cities, regions, states, or countries that are affected by the crisis. -- We always allow people to declare themselves into the crisis (or out) in case our geolocation prediction is inaccurate. This means we can be a bit more selective with the geographic area, since we want to be pretty high signal with our notifications. We actually use notification click-through and conversion rates as downstream signals on how well a launch went. -- For something like Paris, we actually just selected the whole city and launched. Especially with the media reporting "Paris terror attacks," this seemed like a good fit.
- smackfu 11y agoFrance is a pretty big country. If you are in Nice, you are a nine hour drive from Paris. It would seem a bit silly to ask if you were okay, and not someone in Belgium who is much, much closer.
- cortesoft 11y agoIt is only about 248 thousand square miles... which is smaller than Texas.
- c22 11y agoI got a safety check because my home city is listed as "Paris", but I was not actually in Paris. I consistently reject requests to share my location though, so it's possible Facebook has more precise information about other users.
- ceph_ 11y ago> The average distance between any two of Facebook’s 1.5 billion users is 4.74 edges Pretty crazy to think about.
- vjeux 11y agoHere's the video from @scale that explains it if you are interested: https://www.youtube.com/watch?v=ptsCWGZW_P8 https://www.youtube.com/watch?v=ptsCWGZW_P8
- xxbondsxx 11y agoHey everyone! FB engineer here who wrote the original code for this and gave the talk during @Scale 2015. There's a recording of our talk here: https://youtu.be/ptsCWGZW_P8?t=333 https://youtu.be/ptsCWGZW_P8?t=333 That's a bit more visual and easier to understand. At the end of the day its really just DFS with seen state and selective exploration :)
- marcusgarvey 11y agoHow does FB decide which disasters qualify for the safety check and which do not?
- tomschlick 11y agoAs described in a post by Zuckerberg, before the Paris attack it was only activated for natural disasters. Paris was the first time it was activated for human disasters and they will be doing it more in the future.
- anandr2013 11y agoI think the post had a bit of a frantic working backwards and managing PR tinge to it. A cyclone/tsunami also takes place over an extended period of time, and is very similar to a human disaster. In any case, it is a really nice feature and the fact that they will start using it for more disasters is undoubtedly a good thing.
- omginternets 11y agoRespectfully, that doesn't answer the question. What is the current policy for determining use?
- rmc 11y agoThe real reason, which they probably can't say, is how much media attention it gets in the USA.
- konstruktor 11y ago> If you are in an area impacted by a disaster Facebook will send you a push notification asking if you are OK. I guess that's great during an earthquake but can be terrible when you're hiding during a terrorist act.
- xxbondsxx 11y agoIf it's any comfort, most people have push notifications turned off for the main Facebook app (understandably since we send quite a few of notifications). However anecdotally some of the survivors of the attacks mentioned that they got phone calls from concerned friends / families while hiding in the Bataclan, which was understandably stressful.
- konstruktor 11y agoIf the safety of your products depends on disabling features, you should stay out of anything remotely safety critical.
- TeMPOraL 11y agoWhat the hell, this can be said about anything. As GP provides an example for, even an unexpected phone call can be unsafe.
- konstruktor 11y agoIn my opinion, "other things are just as bad" is as good an argument as "if you turn it off, it's not dangerous". I still think it's not smart to send push notifications in an active shooter situation for a feature that is made to give people who are not involved peace of mind. If you consider such risks, and not get defensive right away, you will find that solutions can be pretty simple, e.g. a banner inside the app, instead of a notification.
- TeMPOraL 11y agoI think shooting was aready over before people over at Facebook even knew something is going on. I imagine they wouldn't even turn it on before the information hit mainstream news.
- cft 11y agoIncidentally that article implies that Facebook contstantly tracks your geo location even when you do not expressly check in.
- jamesfe 11y agoWe are not OK with the NSA doing this and (theoretically) not viewing the data. We are OK with Facebook doing this and exploiting the data for monetary and market advantages.
- soared 11y agoDon't confuse your opinions with ours.
- mason55 11y agoGenerally people are ok with Facebook doing it because they can opt out. If you notice, the times people really get upset about companies tracking their personal information is if it's either not disclosed or it's done in a shady manner. Also, capitalist societies tend to treat state actors differently than private corporations. It's much easier to choose a new corporation to interact with and the state tends to have a lot more personal/private data about you (which you're required to share with them).
- rmc 11y agoYou can't opt out of Facebook's shadow profiles.
- jonesb6 11y agoYeah ok but how many end-users are conscious enough of the situation to OPT-OUT of such an intrusive policy? On the same vein as accepting every terms and conditions that comes your way, I think most people are severely uninformed about this. It's like how many people believe software engineering is "magic", they believe Facebook or the government will protect them with "magic". Hint: there is no magic.
- bekimdisha 11y agoWhatsApp now uses Facebook Messenger's protocol ... FYI
- tyggy 11y agohow do you know?
- bekimdisha 11y agoWhatsApp now uses Facebook Messenger's protocol ... FYI
- haraldurt 11y ago>The average distance between any two of Facebook’s 1.5 billion users is 4.74 edges. Sorry Kevin. With 1.5 billion users the whole graph can be explored within 5 hops. Nitpicking here, but that does not follow. Starting from a random user and hopping 5 times in all directions you'd expect to explore about half of the graph.
- fnbr 11y agoYour post is technically correct, but I think that you'd be likelier to explore more- say, 80% of the graph. I suspect that there are small pockets of extremely unconnected people which creates a long tail, distorting the mean.
- eggie 11y agoUnless the data can somehow be shared how is anyone to know what the structure is? There is no point in speculating...
- cortesoft 11y agoYeah, I noticed that, too. Just because 4.74 is the average doesn't tell you enough to know how many people you will reach by exploring 5 hops. Also, they clearly are not including unconnected people in their calculation - there are lots of people who are probably unconnected to the general population. I know from when I used to work on facebook apps that I had a few accounts only connected to each other.
- ldesegur 11y agourl seems to be down. Any url for the cached content?
- flashman 11y agoI wonder what Facebook will say when the governments of the world realise they can use this capability to contact their own citizens - especially if Facebook's continued operation in that country is contingent on its cooperation. 'Safety Check' is just the end user experience; the underlying mechanism is a way to propagate messages invasively across a geo-social network. Like any technology, 'good' or 'nasty' depends on how it's used.
- xxbondsxx 11y agoUsually this is enforced at the cellphone carrier level. The US has the amber alert protocol which also has a function for the president to dispatch any message (and can only be used by the president iirc), and that level of message can't be turned off via settings. Even in our best countries FB usage is never 100%, so cellphone / landlines makes a bit more sense.
- dragonwriter 11y ago> The US has the amber alert protocol which also has a function for the president to dispatch any message (and can only be used by the president iirc), and that level of message can't be turned off via settings. This is the Wireless Emergency Alert system, which carries Amber Alerts, Alerts about imminent threats to life/safety, and Presidential Alerts. The last (and only the last) can't be disabled in settings, because the legislation requiring support for the capacity required that Presidential alerts not be disabled. (The system is basically the mobile-device equivalent of the broadcast Emergency Alert System.)
- flashman 11y agoI suppose I hadn't really thought about why they'd use Facebook when you can just message all the cellphones in a geographic area. Your reasoning makes sense.