This is a takeoff on a well known WWII pamphlet, the Simple Sabotage Field Manual.[1]
That's not the real worry today. Today we have to worry about remote sabotage of key systems - water, power, comms. It's quite possible that we will see major blackouts in the US, Russia, Europe, or China as side effects of the various wars in progress.
I'm assuming by "significant" you mean an attack on critical infrastructure.
That's a strategic capability that very likely requires multiple attack chains, not a single exploit. For Western countries, cost is probably the least significant factor in deciding to use it.
One would want to be certain that option is available, but only when absolutely necessary. Using it on a random Tuesday would take that particular option off the table forever. Best case scenario, Russia discovers the means by which the attack was carried out. Worst case, they retaliate with nuclear weapons.
Globally, I believe there are only a few countries capable of executing such a plan.
Hacking would just be tit-for-tat at most, and unlikely to be accepted as a good reason for major escalations. Most likely Russian infrastructure is just too old to be vulnerable in the same ways as Western infrastructure.
But it is not. It's quite real! It makes a lot of sense... it's exactly the type of stuff that frustrates people [because it slows down the organization] but happens a lot [because it's not easily detectable/fireable].
Yeah, professional saboteurs only target key systems since incidental systems are constantly experiencing the kind of "sabotage" the site talks about but mostly through laziness, incompetence and bureaucratic fief assertion.
That's not the real worry today. Today we have to worry about remote sabotage of key systems - water, power, comms. It's quite possible that we will see major blackouts in the US, Russia, Europe, or China as side effects of the various wars in progress.
[1] https://www.cia.gov/stories/story/the-art-of-simple-sabotage...