Page 553 - (ISC)² CISSP Certified Information Systems Security Professional Official Study Guide

word processor process, and the software chooses which thread it
works on at any given moment.

Symmetric multiprocessing systems use threading at the operating

system level. As in the word processing example just described, the
operating system also contains a number of threads that control the
tasks assigned to it. In a single-processor system, the operating system
(OS) sends one thread at a time to the processor for execution. SMP
systems send one thread to each available processor for simultaneous

execution.

Processing Types

Many high-security systems control the processing of information
assigned to various security levels, such as the classification levels of
unclassified, sensitive, confidential, secret, and top secret that the U.S.
government assigns to information related to national defense.
Computers must be designed so that they do not—ideally, so that they
cannot—inadvertently disclose information to unauthorized recipients.

Computer architects and security policy administrators have

addressed this problem at the processor level in two different ways.
One is through a policy mechanism, whereas the other is through a
hardware solution. The following list explores each of those options:

Single State Single-state systems require the use of policy
mechanisms to manage information at different levels. In this type of
arrangement, security administrators approve a processor and system
to handle only one security level at a time. For example, a system

might be labeled to handle only secret information. All users of that
system must then be approved to handle information at the secret
level. This shifts the burden of protecting the information being
processed on a system away from the hardware and operating system
and onto the administrators who control access to the system.

Multistate Multistate systems are capable of implementing a much
higher level of security. These systems are certified to handle multiple

security levels simultaneously by using specialized security
mechanisms such as those described in the next section, “Protection
Mechanisms.” These mechanisms are designed to prevent information