ZyXEL P-660HW-T1 v3 User Guide - Page 207

Security Considerations, Triangle Route

Page 207 highlights

Chapter 10 Firewalls 10.5.3 Security Considerations Note: Incorrectly configuring the firewall may block valid access or introduce security risks to the ZyXEL Device 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? Once these questions have been answered, adding rules is simply a matter of entering the information into the correct fields in the web configurator screens. 10.5.4 Triangle Route When the firewall is on, your ZyXEL Device acts as a secure gateway between your LAN and the Internet. In an ideal network topology, all incoming and outgoing network traffic passes through the ZyXEL Device to protect your LAN against attacks. Figure 84 Ideal Firewall Setup LAN 1 WAN 2 P-660HW-Tx v3 Series User's Guide 207

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Chapter 10 Firewalls
P-660HW-Tx v3 Series User’s Guide
207
10.5.3
Security Considerations
Note: Incorrectly configuring the firewall may block valid access or introduce security
risks to the ZyXEL Device 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?
Once these questions have been answered, adding rules is simply a matter of
entering the information into the correct fields in the web configurator screens.
10.5.4
Triangle Route
When the firewall is on, your ZyXEL Device acts as a secure gateway between your
LAN and the Internet. In an ideal network topology, all incoming and outgoing
network traffic passes through the ZyXEL Device to protect your LAN against
attacks.
Figure 84
Ideal Firewall Setup
1
2
WAN
LAN