Physical access to computers in the late 70s was decently secured. Most computers were at large businesses (typically with access through a lobby with a recepti

Physical access to computers in the late 70s was decently secured. Most computers were at large businesses (typically with access through a lobby with a receptionist watching) or universities with access limited to students & faculty. So there was some security, not usually great, but few bad actors could get access, even across networks. As computers became more common physical-security-only stopped working well.