What Facebook knows about you

Thomas Macaulay
Thomas Macaulay

Thomas Macaulay

Tom is online editor. He studied English Literature and History at Sussex University before gaining a Masters in Newspaper Journalism from City University. He's particularly interested in the public sector and the ethical implications of emerging technologies.


If the advertisements on your Facebook newsfeed appear remarkably relevant, it's because the social network giant knows you very well. Facebook amassed an estimated $39.9 billion in ad revenue in 2017 by mining its vast troves of data on 2.2 billion users and then selling targeted information to advertisers that they use to sell you products and services based on your personal tastes.

There are also more sinister ways companies use your information. Researcher Michal Kosinski devised a model that analysed a user's Facebook "likes" to predict information such as ethnicity, sexual orientation, and political beliefs to both create and locate personal psychological profiles.  

A similar strategy of data analysis may have helped Donald Trump reach the White House.

Read next: What Google knows about you – and how to make it forget

Cambridge Analytica harvested data from an estimated 87 million Facebook users and used the information to send them targeted campaign ads that appealed to their personal needs and desires. Facebook CEO Mark Zuckerberg was called to testify before Congress about the breach.

Wikileaks founder Julian Assange called Facebook "the most appalling spying machine that has ever been invented," in an interview with Russian news site RT.

"Here we have the world's most comprehensive database about people, their relationships, their names, their addresses, their locations and the communications with each other, their relatives, all sitting within the United States, all accessible to U.S. intelligence," claimed Assange.

"Every time you go to a party and take a picture and post that picture to Facebook, you're being a rat," he added at a book launch in 2014.

But even his organisation can't resist joining the mischief. Wikileaks has its own Facebook page with more than 3.5 million followers.

Facebook collects a disturbingly detailed dataset of its users and it hasn't always been transparent about exactly how it's used.

Additional reporting by Laurie Clarke