Approach

Could sandbox (contain) what such invoked code can do at the application level---has still resulted in security issues. Also resource issues. Forcing applications to do what operating system should do.

Authors argue these are operating system, not application issues and should be handled by providing operating system support.

Current Operating System support is inadequate---not enough flexibility. Unix provides coarse permissions of "root", "all", and a single group permission.

Approaches Unix uses to overcome this inflexibility: setuid()/setgid(), chroot().

Unix violates the "principle of least privilege," which states that a process should have access to only the set of object it needs to accomplish a task.

Goal: Flexible security mechanisms that restrict access of system resources to the absolute minimum necessary. How to define and realize?