Nortel BSR252 Configuration - Basics page 170

170 Chapter 11 Firewall screens
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You can define additional rules and sets or modify existing ones, but exercise
extreme caution in doing so.
For example, you can create rules to:
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These custom rules work by comparing the Source IP address, Destination IP
address and IP protocol type of network traffic to rules set by the administrator.
Your customized rules take precedence and override the Business Secure Router
default rules.
NN47923-500
By default, the Business Secure Router stateful packet inspection blocks
packets traveling in the following directions:
WAN to LAN
WAN to WAN/Business Secure Router
This prevents computers on the WAN from using the Business Secure Router
as a gateway to communicate with other computers on the WAN, or to
manage the Business Secure Router, or both.
Note: If you configure firewall rules without a good understanding of
how they work, you can inadvertently introduce security risks to the
firewall and to the protected network. Make sure you test your rules after
you configure them.
Block certain types of traffic, such as IRC (Internet Relay Chat), from the
LAN to the Internet.
Allow certain types of traffic, such as Lotus Notes database synchronization,
from specific hosts on the Internet to specific hosts on the LAN.
Allow everyone except your competitors to access a Web server.
Restrict use of certain protocols, such as Telnet, to authorized users on the
LAN.