Who's Watching You Online?

Facebook's boss Mark Zuckerberg tells the US Congress that users control their data - but do they really? We examine how more information is gathered about you than you might think. And we ask how deeply the University of Cambridge is involved in the Facebook data scandal. Vesselin Popov from the Psychometrics Centre at the university responds. Presented by Rory Cellan-Jones, with BBC tech reporter Zoe Kleinman, and special guest Frederike Kaltheuner from Privacy International.

(Image: Woman looking at data on a computer screen as if seen from behind the glass, Credit: Getty Images).