Should you let websites track your online movements? Vivienne Nunis speaks to Frederike Kaltheuner from Privacy International and investigates the split-second auction process where firms bid to put targeted ads in front of your eyes. We hear from DuckDuckGo, the search engine that promises to protect your privacy, and controversial Israeli firm The Spinner, which uses cookies to subliminally change people’s behaviour.

(Photo: Chocolate chip cookies, Credit: Getty Images)