Listen up, Facebook users: In order to "protect your account" you were once asked to enter your phone number for the platform's two-factor authentication (2FA), and you likely complied.
What you don't realize, however, is that Facebook is using your phone number to target you with ads, and additionally, anyone -- regardless of your privacy settings -- can use your number to look up your profile.
Inside Hook explains that by default, the phone number lookup is set to "Everyone," and though you can change the settings to "Friends of friends" or "Friends," if someone has your phone number, there's no way to completely hide your profile.
Security expert Zeynep Tufekcii explains it perfectly with this tweet:
So, the solution that'd completely ensure your privacy would be to delete your Facebook profile, but if you're not that committed, it's recommended to change your settings so that your phone number lookup is for "Friends."
Or you could simply not use your phone number for 2FA, which has been an option since last May.