ZyXEL Communications 2 Plus User Manual

 Chapter 11 Firewall

ZyWALL 2 Plus User’s Guide

Figure 131   Block VPN to VPN Traffic by Default Example    

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Incorrectly configuring the firewall may block valid access or introduce security 
risks to the ZyWALL and your protected network. Use caution when creating or 
deleting firewall rules and test your rules after you configure them.

Consider these security ramifications before creating a 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?