Page 566 - (ISC)² CISSP Certified Information Systems Security Professional Official Study Guide

manufacturer. Some of the more common monikers are included in
the following list:

Privileged mode

Supervisory mode

System mode

Kernel mode

No matter which term you use, the basic concept remains the same—
this mode grants a wide range of permissions to the process executing
on the CPU. For this reason, well-designed operating systems do not
let any user applications execute in privileged mode. Only those

processes that are components of the operating system itself are
allowed to execute in this mode, for both security and system integrity
purposes.

Don’t confuse processor modes with any type of user access

permissions. The fact that the high-level processor mode is
sometimes called privileged or supervisory mode has no
relationship to the role of a user. All user applications, including
those of system administrators, run in user mode. When system
administrators use system tools to make configuration changes to

the system, those tools also run in user mode. When a user
application needs to perform a privileged action, it passes that
request to the operating system using a system call, which
evaluates it and either rejects the request or approves it and
executes it using a privileged mode process outside the user’s
control.

Memory

The second major hardware component of a system is memory, the
storage bank for information that the computer needs to keep readily

available. There are many different kinds of memory, each suitable for
different purposes, and we’ll take a look at each in the sections that
follow.