ZyXEL Communications P-320W, User Manual

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P-320W User’s Guide
Chapter 9 Firewall 109
C
H A P T E R
9
Firewall
This chapter gives some background information on firewalls and explains how to get started
with the Prestige firewall.
9.1 Introduction to Firewall
9.1.1 What is a Firewall?
Originally, the term firewall referred to a construction technique designed to prevent the
spread of fire from one room to another. The networking term "firewall" is a system or group
of systems that enforces an access-control policy between two networks. It may also be
defined as a mechanism used to protect a trusted network from an untrusted network. Of
course, firewalls cannot solve every security problem. A firewall is one of the mechanisms
used to establish a network security perimeter in support of a network security policy. It
should never be the only mechanism or method employed. For a firewall to guard effectively,
you must design and deploy it appropriately. This requires integrating the firewall into a broad
information-security policy. In addition, specific policies must be implemented within the
firewall itself.
9.1.2 Stateful Inspection Firewall.
Stateful inspection firewalls restrict access by screening data packets against defined access
rules. They make access control decisions based on IP address and protocol. They also
"inspect" the session data to assure the integrity of the connection and to adapt to dynamic
protocols. These firewalls generally provide the best speed and transparency; however, they
may lack the granular application level access control or caching that some proxies support.
Firewalls, of one type or another, have become an integral part of standard security solutions
for enterprises.
9.1.3 About the Prestige Firewall
The Prestige firewall is a stateful inspection firewall and is designed to protect against Denial
of Service attacks when activated (click
the General tab under Firewall and then click the
Enable Firewall check box). The Prestige's purpose is to allow a private Local Area Network
(LAN) to be securely connected to the Internet. The Prestige can be used to prevent theft,
destruction and modification of data, as well as log events, which may be important to the
security of your network.
The Prestige is installed between the LAN and a broadband modem connecting to the Internet.
This allows it to act as a secure gateway for all data passing between the Internet and the LAN.