3Com 3C16111 - SuperStack 3 Firewall Web Site Filter, Руководство пользователя

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Using Network Access Policy Rules 157
You must have already registered the Firewall before Activating the Web
Site Filter.
Using Network
Access Policy Rules
Network Access Policy Rules are the tools you use to control traffic
between the LAN, DMZ and WAN ports of your Firewall.
Use this list to help you create rules.
■
State the intent of the rule.
The following are examples of intent for rules:
■
This rule will restrict all IRC access from the LAN to the Internet.
■
This rule will allow a remote Lotus Notes server to synchronize over
the Internet to an internal Notes server.
■
Is the intent of the rule to allow or deny traffic?
■
What is the flow of the traffic: from the LAN to the Internet, or from
the Internet to the LAN?
■
List which IP services will be affected.
■
List which computers on the LAN will be affected.
■
List which 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.
Once you have defined the logic of the rule, it is critical to consider the
security ramifications created by the rule:
■
Will 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 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?
■
Will this rule allow Internet users access to resources on the LAN in a
manner that may create an undue security vulnerability?
For example, if NetBIOS ports (UDP 137, 138, 139) are allowed from
the Internet to the LAN, Internet users may be able to connect to PCs
with file sharing enabled.
DUA1611-0AAA02.book Page 157 Thursday, August 2, 2001 4:01 PM