Page 806 - (ISC)² CISSP Certified Information Systems Security Professional Official Study Guide

Secure Network Components

The internet is host to countless information services and numerous
applications, including the Web, email, FTP, Telnet, newsgroups, chat,
and so on. The internet is also home to malicious people whose

primary goal is to locate your computer and extract valuable data from
it, use it to launch further attacks, or damage it in some way. You
should be familiar with the internet and able to readily identify its
benefits and drawbacks from your own online experiences. Because of
the success and global use of the internet, many of its technologies

were adapted or integrated into the private business network. This
created two new forms of network segments: intranets and extranets.

An intranet is a private network that is designed to host the same
information services found on the internet. Networks that rely on
external servers (in other words, ones positioned on the public
internet) to provide information services internally are not considered
intranets. Intranets provide users with access to the web, email, and

other services on internal servers that are not accessible to anyone
outside the private network.

An extranet is a cross between the internet and an intranet. An
extranet is a section of an organization’s network that has been
sectioned off so that it acts as an intranet for the private network but
also serves information to the public internet. An extranet is often
reserved for use by specific partners or customers. It is rarely on a

public network. An extranet for public consumption is typically labeled
a demilitarized zone (DMZ) or perimeter network.

Networks are not typically configured as a single large collection of
systems. Usually networks are segmented or subdivided into smaller
organizational units. These smaller units, grouping, segments, or
subnetworks (i.e., subnets) can be used to improve various aspects of
the network:

Boosting Performance Network segmentation can improve

performance through an organizational scheme in which systems that
often communicate are located in the same segment, while systems