ZyXEL Communications G-2000 Plus User Manual

ZyAIR G-2000 Plus User’s Guide

Chapter 15 Firewall Screens

194

Once the logic of the rule has been defined, it is critical to consider the security ramifications 
created by the rule:

1 Does 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?

2 Is 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?

3 Does a rule that allows Internet users access to resources on the LAN create a security 

vulnerability? For example, if FTP ports (TCP 20, 21) are allowed from the Internet to the 
LAN, Internet users may be able to connect to computers with running FTP servers.

4 Does this rule conflict with any existing rules?

Once these questions have been answered, adding rules is simply a matter of plugging the 
information into the correct fields in the web configurator screens.

Should the action be to Block or Forward?

Note: “Block” means the firewall silently discards the packet.

Select the service from the Service scrolling list box. If the service is not listed, it is necessary 
to first define it. See “Predefined Services” on page 206 for more information on predefined 
services.

What is the connection’s source address; is it on the LAN or WAN? Is it a single IP, a range of 
IPs or a subnet?

What is the connection’s destination address; is it on the LAN or WAN? Is it a single IP, a 
range of IPs or a subnet?