From refrigerators to cars: how can hackers break into internet-connected devices?

From refrigerators to cars: how can hackers break into internet-connected devices?

A cyber attack that shut down cooling systems in hundreds of supermarkets in France has highlighted the dangers of hacking internet-connected devices, from refrigerators and surveillance cameras to cars and heating systems. How can hackers control these devices, and what information can they steal? To what extent are electricity and water networks exposed to danger?