If you use Facebook, your phone number may not be as private as you think.
A way in which Facebook privacy can be abused has come to light that will shock many users, but that the social network itself seems to consider a deliberate feature.
If you enter someone's phone number into the search box on Facebook, the site can perform a reverse look-up and tell you who the phone number belongs to.
You can see in the screenshot how I entered the mobile phone number of someone I am not Facebook friends with, and instantly was offered their name, photograph and a link to their profile.
When I spoke to the Facebook user in question, she was shocked and surprised that I had been able to find her profile simply by entering her mobile phone number.