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Topologies and IDS • Chapter 7 441

TEST DAY TIP

The terminology can be confusing to beginners. One might think the
internal network would be the Internet, but this is not the case. An
Internet (including the global Internet) refers to communications
between different networks, while the intranet refers to communica-
tions within a network. It may help to use a comparison: interstate com-
merce refers to business transacted across state lines (between different
states), while intrastate commerce refers to business transacted within
one state.

Figure 7.8 A Simple Intranet Example
Intranet

The Internet Server Server
and DMZs
Switch
Last Firewall from
the Internet

Workstation Workstation

It is expected that all traffic on the intranet will be secure and safe from the
prying eyes on the Internet. It is the network security professional‘s job to make
sure that this happens.While a security breach of a DMZ system can be costly to a
company, a breach that occurs inside an intranet could be extraordinarily costly and
damaging. If this happens, customers and business partners might lose faith in the
company’s ability to safeguard sensitive information, and other attackers will likely
make the network a favorite target for future attacks.
To ensure that all traffic on the intranet is secure, the following issues should be
addressed:

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