As if you needed more reason to despise Facebook, Kashmir Hill reports on Facebook’s truly garbage practise of violating your contacts information without disclosing that’s what they’re doing.
Facebook is not content to use the contact information you willingly put into your Facebook profile for advertising. It is also using contact information you handed over for security purposes and contact information you didn’t hand over at all, but that was collected from other people’s contact books, a hidden layer of details Facebook has about you that I’ve come to call “shadow contact information.” […]
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.”