It was exactly like the movie Hackers. 😅

Due to the nature of how the ARPAnet was born (lots of academic influence and the view of free sharing of information) outside the DOD infosec wasnt a thing, even then it was an after thought.

There was a healthy phone hacking community coming out of the 70s and into the 80s. Their techniques for getting free calls helped with exploiting the ARPAnet

There were pretty significant technology changes in the 90s with the WWW and the number of people and companies online leading to more opportunities and ways to exploit.

Wargames and Sneakers are pretty entertaining and while movies will give you a bit of a vibe.

If you can highly recommend you read

https://en.wikipedia.org/wiki/The_Cuckoo's_Egg_(book)

Really easy read and amazing true story

Long kiss goodnight