ZyXEL Communications P-870HW-I Series, User Manual

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P-870HW-I1 User’s Guide
Chapter 11 Firewalls 147
C
H A P T E R
11
Firewalls
This chapter gives some background information on firewalls and introduces the ZyXEL
Device firewall.
11.1 Firewall Overview
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.
11.1.1 Stateful Inspection Firewalls
Firewalls, of one type or another, have become an integral part of standard security solutions
for enterprises. 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.
11.1.2 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. 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. The ZyXEL Device also has packet filtering
capabilities.
The ZyXEL Device is installed between the LAN and the Internet. This allows it to act as a
secure gateway for all data passing between the Internet and the LAN.
The ZyXEL Device has one DSL port and four Ethernet LAN ports, which physically separate
the network into two areas.