There were recently serious earthquakes in Japan and Ecuador. Earthquake sensors are meant to send messages to shut down utilities in an affected area, preventing further destruction and potentially saving lives.
Unfortunately, smart cities present the ideal target for hackers to create bot-net style networks of compromised devices, and use them to disrupt critical public services. If a bad actor replaces an authentic sensor with a rogue device, any data from that device would not be trustworthy. But to know that the data’s bad, you’d have to be able to detect that the device itself has become a “bad actor”.
The risk isn’t just theoretical; traffic lights and the smart grid are vulnerable too.