We all have our cellphone number connected to our Facebook or we have some form of the Facebook Apps on our phone. But do we really know what Facebook uses it for? I bet you don’t!

In February 2014, Facebook was officially launched. The ideas we’re simple: You add a friend, they accept you and their friends would then be added to your “People You May Know” list. Later it started to become a bit more complex with Facebook asking permission to look through your e-mail’s address book to find people you might know. Today it is no longer that simple and Facebook no longer uses only your data to determine these lists.

In 2013 and 2014, Facebook revamped their whole privacy system. You got more control over who sees what on your profile and who sees individual posts on your timeline. All good things comes at a price though and Facebook shortly followed with a revised version of terms and conditions for Facebook users. For a short while users protested by posting statuses they believed indemnified them against these changes in Facebook’s Terms and Conditions, with no effect.

I recently got asked the question “What is Facebook’s Policy on the use of your cellphone number”. Facebook was always very clear in the regard that it will not distribute your cellphone number, but they can and probably will use it without your consent (to enhance your experience, of course). A question on a security forum on Stack Exchange, a popular IT Q&A forum, recently posed the question “Can Facebook suggest contacts based on your cellphone number”. Some answered yes, some answered no. I decided to investigate.

Because my personal Facebook profile already has too many elements that can influence my People You May Know list, I decided that it will be best to perform this investigation using a temporary, brand new Facebook account. To ensure that my results were accurate, I cleared my browser cache, logged out of my personal Facebook and delisted my cellphone number off my personal account. I then created a new, free email account to act as the email account of my test account so I could be sure that I have no contacts within it.

Logging into my new Facebook account not only gave me that fresh “starting over” feeling, but I immediately noticed that I have no suggestions for friends. Since it is simply a fake account, I proceeded to add a fake cellphone number to my account before even trying to add any friends, with one problem; Facebook requires cellphone number confirmation, which I could not perform. So I added my real cellphone number to the mix and verified it.

Upon clicking on the Home button, I immediately felt like Facebook somehow got hold of my whole life story when suddenly my People You May Know list was packed with people I already know. As I am extremely concerned with my privacy, I immediately started mentally listing the possibilities. My first thought was that Facebook somehow used my cellphone number to get the contacts on my cellphone, but 2 things held the thought back; It’s technically not quite possible without me having some sort of app that can connect Facebook to my phone and I didn’t have numbers for some of the people on the list. That’s when it hit me… The reverse is possible. I contacted the top friends on the list and asked if they have my cellphone number stored on their phone and if they do, whether they have the Facebook mobile app. Their answers we’re all yes.

So there it was, the shocking truth that Facebook keeps a record of the contact numbers on my Facebook friends’ phones using the app and once someone joins Facebook with a number that matches, the phone’s owner gets listed as someone the new user might know. How’s that for advanced technology and big data use?

Of course Facebook didn’t even respond to my request for a comment on whether my theory is correct that they are using our cellphone numbers and Facebook App for this purpose, so I will continue my investigation into it. My question is just: How would you feel if it was true? Are you happy with Facebook using your phone’s contact list and number for this reason? Join the discussion! Comment in the comments section below, please.