"Evil" app shows how Facebook users make their mobile numbers public

Back in the early cretaceous period – ok, make that 2006 – users of Facebook thought they were using a private social network. As a result they did all sorts of things which they probably wouldn’t have made public. Of course, now we know that Mark Zuckerberg believes that “if people share more, the world will become more open and connected”. In plain English that means Facebook wants to open up much of your data to the outside world, assuming you haven’t gone through your privacy settings with a fine-toothed comb. That may also include your mobile phone number.

Because, in the past (and even today), many Facebook users who lost their mobile phone unwisely created groups often called “lost my phone!!!!! need ur numbers!!!!!” or similar.

They then ask their friends to post their mobile numbers onto the group. Their friends have obliged. Most of these groups are marked as ‘public’, or ‘visible to everyone’ but they would have been much harder to access or scrape before Facebook began opening up.

And as we all now know “Public” on Facebook effectively means “On Google”.

It is therefore childs’ play to Google for mobile numbers publicly shared on Facebook.

But that would be dull and easy. Instead, London-based developer Tom Scott has created a Web app called, simply, Evil.

This randomly displays the private phone numbers of unsuspecting Facebook users.

Evil uses the graph API to search for groups about lost phones. It picks them at random, extracts some of the phone numbers, and then shows them. However, in an act of mercy not usually associated with “evil”, it replaces the last three numbers with XXX. The results are not stored and all the processing happens on your own computer.

So, in case you posted to one of these ‘lost phone’ groups, the only way to make your phone number private on Facebook is to go into all the “lost number” groups you’ve ever joined and delete your posts.

Of course, some people should just take more notice of what they put online. But then most people don’t…