ZyXEL Communications P-2802H-I Series, Руководство пользователя

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P-2802H(W)(L)-I Series User’s Guide
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H A P T E R
11
Firewalls
Use these screens to enable and configure the firewall that protects your ZyXEL Device and
your LAN from unwanted or malicious traffic.
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 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.
11.1.2 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 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.
Enable the firewall to protect your LAN computers from attacks by hackers on the Internet and
control access between the LAN and WAN. By default the firewall: