We have created the ultimate hive-mind robot: an Internet of interconnected devices that senses, thinks and acts. Bruce Schneier calls it the "World-Sized Web". It includes everything from driverless cars to smart thermostats, from billboards that respond to specific people to drones equipped with their own behavioural algorithms. While the World-Sized Web carries enormous potential, Schneier argues that we are unprepared for the vulnerabilities it brings. Cutting-edge digital attackers can now crash your car, pacemaker and home security system and everyone else's.