Obviously there were people with unauthorized access to networks and devices as depicted in the movie War Games going many years back. I mean more how countries (such as the US and China) actively try to break into each other's sensitive systems (banking, defense, power, etc.).

I recently saw an episode of The Americans where the Soviets physically attacked ARPAnet, but I don't mean this type of attack.

Attacks originating from foreign soil to a country using only electronic bits of data. Do we know when this started? Or when was it first reported by a country?

Living in the US gives me the feeling that, beyond the NSA transgressions, there has been a good number of other incidents in the past I've never heard of.