ZyXEL Communications ZyAIR G-2000 Plus, Руководство пользователя

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ZyAIR G-2000 Plus User’s Guide
Chapter 15 Firewall Screens 194
15.3.2 Security Ramifications
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.
15.3.3 Key Fields For Configuring Rules
15.3.3.1 Action
Should the action be to Block or Forward ?
15.3.3.2 Service
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.
15.3.3.3 Source Address
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?
15.3.3.4 Destination Address
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?
Note: “Block” means the firewall silently discards the packet.