Have you ever created a Facebook group called, “I lost my phone and need your phone numbers!”, or something similar? If so, you may have just made all of you and your friends’ phone numbers public. Leveraging the new Graph API, Tom Scott developed an interesting tool which crawls public Facebook groups for the phrase “lost phone” and then collects the phone numbers of all the users.
As Tom Scott pointed out to Mashable, this isn’t exactly something that you couldn’t do using Google, it’s just that automatic the process appears to be much more “Evil”, hence the name of the tool (which can be found here). Right now Tom Scott is not displaying the full phone numbers as the purpose of this was simply to demonstrate what types of things can be done using the Graph API.
However, any company which is looking to harvest user data will have a field day parsing through this type of information, if they aren’t doing so already. Ultimately, Facebook isn’t really at fault for this information showing up. Instead, it’s the users who posted their contact information within a group, without necessarily realizing that the group was completely public.
Perhaps Facebook could alert users that before they post on a wall in a public group, that information will be available for anybody to see. You can see how the service works via the video below. If you want to try it out yourself, you can do so by going here.