Facebook won't keep your two-factor phone number truly private

He added that, perhaps unsurprisingly, this data is also shared with WhatsApp and Instagram, which means your phone number becomes a unique ID for you.

Facebook told TechCrunch that this is not a new situation, which is true, and we've known that the platform uses phone numbers for ad tracking since last September. The company uses that unique ID, since it's tied to you, and can use it to sell ads, much as it does with everything else it knows about you.

Third-party systems, like Google Authenticator and Duo Security can also be used to add an additional layer of protection onto your account.

The fact that Facebook accounts are searchable purely with a phone number raises some interesting privacy and security concerns. It's possible to limit this to just your circle of friends, but it's set to everyone by default, which could lead to unwanted lookups.

After training to be an intellectual property lawyer, Dan abandoned a promising career in financial services to sit at home and play with gadgets. One day, if he's very, very lucky, he'll live out his dream to become the executive producer of Doctor Who before retiring to Radio 4.