Cambridge Analytica's harvesting of 50 million Facebook profiles

In 2015, Facebook removed a feature that had been in place for some years that allowed developers to access information about Friends who had also signed up for their app. During that time, about 270,000 people downloaded and installed an app that was portrayed as part of an online personality quiz that offered a small payment to users who completed it. That app, This Is Your Digital Life, allowed University of Cambridge researcher Aleksandr Kogan to harvest data on an estimated 50 million Facebook users in the space of a few weeks. Users were told the data was for academic research. Later Facebook admitted 87 million users had their data harvested.

Facebook's policies at that time prohibited Kogan from selling or sharing the data with third parties without consent, and also barred collecting Friends' data for any purpose other than improving the in-app user experience. Nonetheless, Kogan passed the data to Cambridge Analytica, which  was able to match it to other data sources to build about 30 million detailed profiles of American and British voters during the 2016 US Presidential election and the EU referendum's Vote Leave campaign. The test results and Facebook data also enabled the company to build models and an algorithm that could analyze profiles and identify personality traits linked to voting behaviour.

Facebook learned of the breach of its policies in 2015. In 2016, it sent letters asking those holding copies of the data to confirm that it had been destroyed. However, it does not appear to have enforced the request by checking forensically that it had been deleted. The company did not report the discovery as a data breach in accordance with the laws of the state of California, where Facebook has its headquarters, on the basis that it was not a data breach but data misuse by third parties. In 2018, after the Guardian and the New York Times revealed the links between Facebook, Cambridge Analytica, and the elections, the US Federal Trade Commission began investigating the question of whether Facebook had violated their 2011 consent decree. 

https://www.theguardian.com/news/2018/mar/17/cambridge-analytica-facebook-influence-us-election

tags: Facebook, Cambridge Analytica, Aleksandr Kogan, FTC, This Is Your Digital Life, apps, social networks, social graph, mathematics
Writer: Carole Cadwalladr and Emma Graham-Harrison
Publication: Guardian