P-2602H(W)(L)-DxA Series User’s Guide
Note: If you configure firewall rules without a good understanding of how they work, you might inadvertently introduce security risks to the firewall and to the protected network. Make sure you test your rules after you configure them.
For example, you may create rules to:
•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.
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 ZyXEL Device’s default rules.
14.3 Rule Logic Overview
Note: Study these points carefully before configuring rules.
14.3.1 Rule Checklist
State the intent of the rule. For example, “This restricts all IRC access from the LAN to the Internet.” Or, “This allows a remote Lotus Notes server to synchronize over the Internet to an inside Notes server.”
1Is the intent of the rule to forward or block traffic?
2What direction of traffic does the rule apply to?
3What IP services will be affected?
4What computers on the LAN are to be affected (if any)?
5What computers on the Internet will be affected? The more specific, the better. For example, if traffic is being allowed from the Internet to the LAN, it is better to allow only certain machines on the Internet to access the LAN.
14.3.2Security Ramifications
1Once the logic of the rule has been defined, it is critical to consider the security ramifications created by the rule:
2Does this rule stop LAN users from accessing critical resources on the Internet? For example, if IRC is blocked, are there users that require this service?
3Is it possible to modify the rule to be more specific? For example, if IRC is blocked for all users, will a rule that blocks just certain users be more effective?
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