Two of Facebook’s own data scientists worked with Kogan between 2013 and 2015, according to the paper. As part of the research, which was separate from Kogan’s work for Cambridge Analytica, Facebook provided Kogan with data on 57 billion Facebook friendships, according to the paper.
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Facebook then provided the authors with data “on every friendship formed in 2011 in every country in the world at the national aggregate level.” The data set included a total of 57,457,192,520 friendships, according to the paper.
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Kogan wrote in the email that he wanted to create statistical models that could accurately identify people at risk for various diseases and illnesses by examining their Web browsing and purchase behaviors, and combine that with medical data from Harvard.

Source: Facebook had a closer relationship than it disclosed with the academic it called a liar – The Washington Post
In all Facebook gave away personal data on potentially 1.5 billion user accounts containing

“Your name. Your location. All your friends. Your family. Your work history. Your schooling. Your birthday. Your checkins. Your events. Your hometown. Your likes, photos. Your relationships. Your religion and politics. And not just for you, but for one [and] a half billion other people.”

This was not a “data breach” – Facebook literally gave it away. Today, we have no idea who has this data on file or what risks may now apply to 1.5 billion people because of it. Read the 1.5 billion link – huge data security vulnerability was exposed and Facebook has no way of knowing what happened. And it happened specifically because of Facebook’s lax approach to security, not because of Kogan.
Kogan also attempted to link in medical and mental health records, and genetic data. Two Facebook staff researchers also worked with Kogan. Kogan tried to share his large data collection with other researchers.
Our online social media data is linked to offline purchase records, through data aggregators like Axciom, typically through the phone number provided “to protect our account”. This enables third parties, or Facebook, to know everything about us from our interests (via likes and group memberships) to our offline purchases at the local grocery story.