ZyXEL Communications NBG-417N, Руководство пользователя, Страница: 141 / 279

Chapter 13 Firewall
User
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13.1.2 What You Need To Know
The following terms and concepts may help as you read through this chapter.
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 a network that is not trusted. 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.
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.
About the NBG4115 Firewall
The NBG4115 ’ s firewall feature physically separates the LAN and the WAN and
acts as a secure gateway for all data passing between the networks.
It 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 NBG4115's purpose is to allow a
private Local Area Network (LAN) to be securely connected to the Internet. The
NBG4115 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 NBG4115 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.
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