In this chapter, we looked at how the history of Unix evolved from
Multics to the system that it is today. With Unix, unlike with other
operating systems, security was not added as an afterthought: secure
multiuser operation has been a requirement since Unix was created.
But our notion of what "secure
operations" means has changed over time, and with
those changes Unix developers have tried to keep pace.
Today, when the majority of Unix systems are effectively single-user
workstations, Unix security depends far more often on code quality
and administrative practices. That's good news, as
it means that Unix is fundamentally securable. However, keeping a
Unix system secure can be a lot of work.