ZyXEL Communications P-661HNU-Fx User Manual
Chapter 13 Firewall
ADSL Series User’s Guide
188
13.4 Firewall Technical Reference
This section provides some technical background information about the topics covered in this
chapter.
chapter.
13.4.1 Guidelines For Enhancing Security With Your Firewall
1
Change the default password via web configurator.
2
Think about access control before you connect to the network in any way.
3
Limit who can access your ZyXEL Device.
4
Don't enable any local service (such as Telnet or FTP) that you don't use. Any enabled service could
present a potential security risk. A determined hacker might be able to find creative ways to misuse
the enabled services to access the firewall or the network.
present a potential security risk. A determined hacker might be able to find creative ways to misuse
the enabled services to access the firewall or the network.
5
For local services that are enabled, protect against misuse. Protect by configuring the services to
communicate only with specific peers, and protect by configuring rules to block packets for the
services at specific interfaces.
communicate only with specific peers, and protect by configuring rules to block packets for the
services at specific interfaces.
6
Keep the firewall in a secured (locked) room.
13.4.2 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?
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?
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.
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.
Delete
Select a service in the Blocked Services, and click this to remove the service from the
list.
list.
Clear All
Click this to remove all the services in the Blocked Services list.
Apply
Click Apply to save your changes.
Cancel
Click Cancel to restore your previously saved settings.
Table 54
Security > Firewall > Services (continued)
LABEL
DESCRIPTION