ZyXEL Communications P-334U - Manual (Page 127)

P-334U/P-335U User’s Guide
Chapter 11 Firewall 127
C
H A P T E R
11
Firewall
This chapter gives some background information on firewalls and explains how to get started
with the ZyXEL Device firewall.
11.1 Introduction to Firewall
11.1.1 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.
11.1.2 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.
11.1.3 About the ZyXEL Device Firewall
The ZyXEL Device 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 ZyXEL Device's purpose is to allow a private Local
Area Network (LAN) to be securely connected to the Internet. The ZyXEL Device 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.