Facebook are criminals, maybe not Legally but Morally.

Facebook has confirmed it does in fact use phone numbers that users provided it for security purposes to also target them with ads.

After a research carried out by Giridhari Venkatadri, Piotr Sapiezynski, and Alan Mislove of Northeastern University, along with Elena Lucherini of Princeton University, to see whether information such as contact details could be used by an advertiser for Ad targeting.

Facebook is not upfront about this practice. In fact, when I asked its PR team last year whether it was using shadow contact information for ads, they denied it. Luckily for those of us obsessed with the uncannily accurate nature of ads on Facebook platforms, a group of academic researchers decided to do a deep dive into how Facebook custom audiences work to find out how users’ phone numbers and email addresses get sucked into the advertising ecosystem.


The researchers also found that if User A, whom we’ll call Anna, shares her contacts with Facebook, including a previously unknown phone number for User B, whom we’ll call Ben, advertisers will be able to target Ben with an ad using that phone number, which I call “shadow contact information,” about a month later. Ben can’t access his shadow contact information, because that would violate Anna’s privacy, according to Facebook, so he can’t see it or delete it, and he can’t keep advertisers from using it either.


The lead author on the paper, Giridhari Venkatadri, said this was the most surprising finding, that Facebook was targeted ads using information “that was not directly provided by the user, or even revealed to the user.”

A post on Gizmodo by Kashmir Hill

When Facebook was asked to confirm or rebuke the claims, a statement by The Social Network Giant said,

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 “We use the information people provide to offer a better, more personalized experience on Facebook, including ads. We are clear about how we use the information we collect, including the contact information that people upload or add to their own accounts. You can manage and delete the contact information you’ve uploaded at any time.”

It was found that when a user gives Facebook a phone number for two-factor authentication or in order to receive alerts about new log-ins to a user’s account, that phone number became targetable by an advertiser within a couple of weeks. So users who want their accounts to be more secure are forced to make a privacy trade-off and allow advertisers to more easily find them on the social network.

There are certainly creepier practices happening in the advertising industry, but it’s troubling this is happening at Facebook because of its representations about letting you control your ad experience. It’s disturbing that Facebook is reducing the privacy of people who want their accounts to be more secure by using the information they provide for that purpose to data-mine them for ads.

Ubon Patrusm

Ubon Patrusm

A mechanical Engineer who have great passions for gadgets.