Earlier quoted context omitted.
> If you can make power usage unexpectedly go up by more than ~10% within a minute, most power grids will fail. Wouldn't that behave identically to a sudden loss of generation? The power grids I know of have schemes to deal with that, by automatically shedding large blocks of load in several stages.
Yes - but IMO, as soon as you've shed any significant amount of load, you've failed. If just 10% of a nationwide grid is down, there's a good chance the phone network won't work, internet will be down, trains won't run, credit card/payment systems won't work, etc. All those things have primary and backup systems, but somewhere in the chain of dependencies there will be both a primary and backup that have been shed, a…
A major infrastructure cyberattack seems effective either as an opening salvo in a traditional military war or to multiply the chaos after a terrorist attack. Taking out the power grid would worsen traffic congestion and create increased demand on emergency services in the short term, and have major economic impacts and high visibility in the long term.