A few weeks ago, anonymous hackers attacked the computers that run the public transport system of San Francisco, which wouldn't take any payments from passengers. The hackers demanded a ransom of 100 Bitcoin (about $73,000) but didn't get any money. Full story here, by Jack Stewart.
If I'm not mistaken, this is the first case a cyber-attack targets a public transport system. Certainly, this will not be the last one. This kind of event is likely to become more common as cities adopt 'smart' strategies of urban management that increasingly connect public services to integrated systems and the 'internet of things'.
Perhaps a good topic for a PhD project, if anyone is interested.