[horeszko]

Regardless of what should or should not be considered an act of war, cyber attacks in practice are in a de facto grey area. Something less than war, but something the US will sanction the leadership and units involved for.

Sandworm by Andy Greenberg is a good book to get the details on how "persistent threat actors" (i.e. state sponsered hackers) are handled by the US government (tldr the US government's calculus is that the grey area suits them for their own offensive cyber operations, and therefore there is a degree of tolerance for foreign PTAs).