The website Junkee put it like this: "You know that one friend who’s always warning you that Facebook is harvesting all your data to subtly manipulate your thoughts? As it turns out, they were kind of right." Facebook, it has transpired, published targeted content based on user profiles that users did not know were shared with third parties. This content was used by the Donald Trump campaign and by pro-Brexit lobbyists to sway voters in their favour. Apparently it succeeded. Here’s how it worked, according to Junkee. In 2014, Aleksandr Kogan made an app called thisisyourdigitallife, which 270,000 people downloaded. If they had read the fine print, they would have realised they had given him access to data they shared on Facebook. Kogan went further. He gained access to information from their friends. In the end, he had the data of 50m people at his fingertips. He sold this to Cambridge Analytica, a firm that specialises in manipulating people based on their data. Cambridge Analytica...

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