Cyber Security Essentials

26 Cyber seCurity essentiAls

up a firewall depend on the type of firewall. ere are three basic types

of firewall: packet-filtering firewalls, stateful firewalls, and application

gateway firewalls. While each of these different firewall types performs

the same basic operation of filtering undesirable traffic, they go about the

task in different manners and at different levels of the network stack.

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While Exhibit 1-13 identifies the firewall as a separate physical device

at the boundary between an untrusted and trusted network, in reality a

firewall is merely software. is does not mean that physical, separate

devices are not firewalls, but merely that these devic ...