How Facebook (ab)uses your mobile number!

Michael de Groot
6 min readMar 15, 2022


I am receiving quite a few notifications on the Facebook mobile app (although I don’t look that often), asking me to do something with my mobile number, well I didn’t think I had it on there, in fact I don’t have it on my profile, but in researching further I discovered it’s there in the background, stupid me. More about that in a bit, but first a few things to share for context.

I am not a big fan of Facebook and I am very suspicious of Mark Zuckerberg. He is exactly the same as any dictator who has ever lived and lied his way into becoming a billionaire, just think about it.

Facebook had 2.912 billion monthly active users as of January 2022, placing it 1st in ranking of the world’s most ‘active’ social media platforms. Nearly 3 billion people on the globe have happily shared their email and very likely their mobile number with Facebook. This data that we have so willingly shared is a forever unlimiting goldmine for Facebook, it’s shareholders and it’s advertisers. Facebook’s monthly active users equate to 36.8% of all the people on Earth today. I call that a pretty big dictatorship!

They (Facebook) have been accused of so many data crimes, but have never been prosecuted and nobody has gone to jail, okay they’ve had a few minor fines, which basically was pocket change for them. You can read the whole timeline of their crimes here: A timeline of trouble: Facebook’s privacy record and regulatory fines, by Guild ~ 4 August, 2021

Image Credit: Facebook’s Monthly Active Users Over Time February 2022 DataReportal

I have known for quite a long time that Facebook’s customers, that is the advertisers, not the users, have many privileges. One of the biggest one of those privileges is “custom audiences”. I have never advertised on Facebook, so I can’t give you the technical ins and outs, you can discover that for yourself, except to highlight that advertisers can upload either email addresses or mobile numbers to Facebook and they will do the happy job of matching them with the existing users on the platform.

Mark Zuckerberg has always claimed they don’t sell user data and in the true sense of that actual term, he’s probably correct, I’m sure in a court of law he would win that argument. But what do you call the matching up of data that Facebook has collected and telling its advertisers that they will do a match for them, as long as they upload the data they themselves have collected. TIP: If a website form asks for your mobile number, NEVER share it, even if it means you can’t go further on that form or at least demand that it should be optional only.

Let’s examine it all in a bit more detail, below is the actual help link from Facebook on why they need your mobile number. I’ve even included the link to the page, so if for whatever reason it gets revised/updated, you can read the latest version there.

We may use your mobile phone number for purposes such as:

  • Helping you log in. If you forget your password or the email address that you use to log in to Facebook, you can look either of them up by entering the mobile number associated with your account.
  • Sending you SMS notifications for updates about activity on your account, promotions and account safety. SMS notifications can help keep your account safe through opt-in features such as two-factor authentication and text message alerts for unrecognised logins. You can opt out of all SMS notifications at any time.
  • Connecting you to other people and content on our platforms through features such as People you may know.
  • Providing and improving ads for you and others. We match your contact information with information that we get from other sources (e.g. when you make a purchase after seeing an ad on Facebook). This helps us improve our ads services for everyone within the Facebook community.

We don’t ever sell personal information, including your mobile phone number, to anyone. Bear in mind that you can control who can see your phone number and who can look you up on Facebook. Learn more about how Facebook uses your phone number in our Data Policy.

We may ask you to confirm your mobile phone number because:

  • You previously added the phone number that we’re asking you to confirm.
  • Time has passed since you last added or updated your phone number.
  • We’ve received information from your device that helps us suggest the number connected to that device.
  • You haven’t added one yet, and we want to show you how.

Bear in mind that the phone number we’re asking you to confirm will only be added to your account if you choose to add it.

Note: Once you’ve confirmed your phone number, you can adjust notification settings and control who can see your contact info. You can also remove a confirmed mobile phone numberfrom your account at any time.

The KEY sentence in the above help guidelines is of course: [“ We match your contact information with information that we get from other sources (e.g. when you make a purchase after seeing an ad on Facebook). This helps us improve our ads services for everyone within the Facebook community.”]

The following are the instructions to advertisers: [ “When we’ve finished hashing your customer list information, we’ll let you know that your audience is ready to use. Once ready, you can immediately create an ad to reach your new Custom Audience, or create a Lookalike Audience to find new people who share similar behaviours and interests with your existing customers.”]

You don’t even need to have been a customer of someone, if any business who advertises on Facebook has managed to get hold of your mobile number, they can upload it onto Facebook and start targeting you with ads, plus it allows them to target others who are ‘alike’. The “hashing” they explain as, [ “ is a type of cryptographic security method that turns your identifiers into randomised code and cannot be reversed.”]

It’s good that they hash the data, i.e. nobody can then export it and use it for other means, but the damage has already been done, if someone has collected your information via a form and then uses that data (mobile phone numbers) to target you specifically with ads, it means that the advertiser has some “legitimate” advantage in getting very very close to you. I’m just not comfortable with this method of advertising and it’s something Facebook provides and supports. I for one will stop providing my mobile number to Facebook and stop providing it to businesses in their forms with the exception of course to certain payment providers. The difficulty we are all facing is that more and more websites are moving towards 2-factor authentication, which means we must provide our mobile number for text messages with codes or you can try and use an authenticator app, although I must admit I have always failed with these app for some reason, they just don’t work reliably at all.

I have provided for you below some instructions on how you can remove your mobile number from Facebook.

To remove a mobile phone number:

  1. Click in the top right of Facebook.
  2. Select Settings & privacy, then click Settings.
  3. Click Mobile in the left column.
  4. Click Remove below the number that you’d like to remove.
  5. Click Remove Number to confirm.

WARNING: Never engage in the apparent “FUN” quizzes that people share that expose what type of flower you are or who your ideal partner is or some other ridiculous click bait that has you sharing your details either in or outside of Facebook. They are invariably hackers trying to spoof your account and post dangerous content on your feed and either tag all your connections or send them messenger messages with the same suspicious content, that could cause malware on their machines.

DISCLAIMER: Removing your mobile number from Facebook must be your own decision, I am merely providing you with some information, so you know what happens inside their advertising ecosystems, it’s better to be informed instead of remaining ignorant. The whole reason why we can use these social media platforms for free are due to the data they can harvest from us to their benefit.

Any questions, let me know.

Originally published at on March 15, 2022.



Michael de Groot

Creator, Certified IPTPA Pickleball Instructor, Taiko Drummer |