If you want to truly have an aneurism (wow, I can't believe I spelled that correctly on the first try! I was sure the computer would have to correct me.), read The Cuckoo's Egg, by Cliff Stoll. It might be the first book about hacking; it was published in the 80s. You might recognize the name of a well-known Unix engineer at a government agency as they try to track the hacker's origin.
Anyway, as you alluded, everything was wide open. The author ponders the amount of trust that was accepted at the time. Nothing surprising, but it still made me say, "wtf" to myself as I read it. Very low skill was needed at the time, relative to modern systems. I guess this is why social engineering is such an effective pathway today.
