Guesswork
Really, who knows.
Its often difficult accurately identifying an attacker (misdirection is a thing).
Hard to know how well key "cyber" infrastructure in a given country is defended unless you try and attack it!
You have no idea what weapons are in someone's arsenal until they actually use them (and that attack actually gets detected..)
I certainly would not underestimate the capabilities Russia, China and Israel, for example, may have
Biting the hand that feeds IT
