Page 1438 - (ISC)² CISSP Certified Information Systems Security Professional Official Study Guide

resources through the use of primary storage. The most common
example of virtual storage is the RAM disk that presents itself to

the operating system as a secondary storage device but is actually
implemented in volatile RAM. This provides an extremely fast
filesystem for use in various applications but provides no recovery
capability.

Random access storage allows the operating system to request
contents from any point within the media. RAM and hard drives

are examples of random access storage resources.
Sequential access storage requires scanning through the entire

media from the beginning to reach a specific address. A magnetic
tape is a common example of a sequential access storage resource.

Volatile storage loses its contents when power is removed from the
resource. RAM is the most common type of volatile storage
resource.

Nonvolatile storage does not depend upon the presence of power

to maintain its contents. Magnetic/optical media and nonvolatile
RAM (NVRAM) are typical examples of nonvolatile storage
resources.

Storage Threats

Information security professionals should be aware of two main

threats posed against data storage systems. First, the threat of
illegitimate access to storage resources exists no matter what type of
storage is in use. If administrators do not implement adequate
filesystem access controls, an intruder might stumble across sensitive
data simply by browsing the filesystem. In more sensitive
environments, administrators should also protect against attacks that
involve bypassing operating system controls and directly accessing the

physical storage media to retrieve data. This is best accomplished
through the use of an encrypted filesystem, which is accessible only
through the primary operating system. Furthermore, systems that
operate in a multilevel security environment should provide adequate
controls to ensure that shared memory and storage resources are set
up with fail-safe controls so that data from one classification level is