If the [inter]national infrastructure goes down, with the firmware on every device on every internet-connected computer bricked at the same time due to a large-scale cyberattack (perhaps followed by a military attack a little while later), we're f-ed.
All this would take is:
- One zero-day each on Windows, MacOS, and Linux.
- Nation-state level resources to create a bricking firmware update for all commonly-used devices.
- Nation-state level resources to create a spreading attack for all major routers and network devices.
- Nation-state level resources to deploy this rapidly enough that response systems can't respond.
With 200 nation-states, it's perhaps just a matter of time....
(And yes, there's a lot more i's to dot and t's to cross, but I think they're all doable, with nation-state level resources)
I think this is more "movie plot", though. "Smart Grid" security has gotten tons better than it was at the start. A lot of very security conscious and smart people have been working on it.
(1) Tank the economy
(2) Likely, be doable with resources totaling in the single-digit million dollars
Modern wars are largely about industrial capacity.
But if it is equally easy to compromise the grid, why not do both?
This may sound like a movie plot, but so did the invasion of Poland at the beginning of WWII, the attack on Pearl Harbor, nuclear bombs on Japan, the rape of Nanjing, or many other actual events which Actually Did Happen.
We tend to underestimate the impact of rare events: our brains are conditioned to discount anything which happens once or less than once per lifetime. That's likely why humanity will kill itself at some point.