Suddenly, the lights across a city go off. There is no warning, and no explanation. People expect the power to come back on, but it doesn’t.People’s mobile phones suddenly stop working. Televisions don’t work. The internet has cut out. Not only can’t the citizens call for help, they can’t find out what’s going on. Panic spreads quickly. A few buildings with back-up power are the only beacons in a blacked-out city. A cyber attack has struck home.Probable? No. Possible? Certainly. Tests have shown that cyber attacks could attack power grids, and knocking out communications is the bread and butter of even relatively low-level cyber attacks.