How much does Facebook know about you? And should you be worried? Newsbeat's James Waterhouse lifts the lid on the data and privacy scandal costing them billions of pounds. Since it came out that a personality quiz on Facebook in 2014 may have led to the personal data of up to 87 million people being taken without their permission - then claims that the data was bought and used by the company Cambridge Analytica for targeted advertising - a lot of people are concerned over what Facebook knows about them. Should we be worried about our Facebook accounts and how much the social network knows about us?