More Facebook sleazy practice

Add “a phone number I never gave Facebook for targeted advertising” to the list of deceptive and invasive ways Facebook makes money off your personal information. Contrary to user expectations and Facebook representatives’ own previous statements, the company has been using contact information that users explicitly provided for security purposes—or that users never provided at all—for targeted advertising.

A group of academic researchers from Northeastern University and Princeton University, along with Gizmodo reporters, have used real-world tests to demonstrate how Facebook’s latest deceptive practice works. They found that Facebook harvests user phone numbers for targeted advertising in two disturbing ways: two-factor authentication (2FA) phone numbers, and “shadow” contact information.

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But the important message for users is: this is not a reason to turn off or avoid 2FA. The problem is not with two-factor authentication. It’s not even a problem with the inherent weaknesses of SMS-based 2FA in particular. Instead, this is a problem with how Facebook has handled users’ information and violated their reasonable security and privacy expectations.

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Even with the welcome move to no longer require phone numbers for 2FA, Facebook still has work to do here. This finding has not only validated users who are suspicious of Facebook's repeated claims that we have “complete control” over our own information, but has also seriously damaged users’ trust in a foundational security practice.

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Second, Facebook is also grabbing your contact information from your friends.

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This means that, even if you never directly handed a particular phone number over to Facebook, advertisers may nevertheless be able to associate it with your account based on your friends’ phone books.

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Even worse, none of this is accessible or transparent to users. You can’t find such “shadow” contact information in the “contact and basic info” section of your profile; users in Europe can’t even get their hands on it despite explicit requirements under the GDPR that a company give users a “right to know” what information it has on them.

  EFF

...but hey, do what you want...you will anyway.