F-SECURE LINUX SECURITY, Manual

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• Responder port : the port on the computer where the connection ends.
Whether the port on the computer is an initiator port or responder port depends on the direction
of the traffic:
• If the firewall service is for outbound traffic, the initiator port is the port on your own computer.
The responder port is then the port on a remote computer.
• If the firewall service is for inbound traffic, the initiator port is the port on a remote computer.
The responder port is then the port on your own computer.
The responder ports are typically mentioned in the software documentation. The initiator port
can usually be any port higher than 1023. However, for some games you may also have to
define specific initiator ports . In this case, they are also mentioned in the software documentation.
If you create a new firewall rule , you have several predefined services that you can add to the
rule. You can also create and add your own services if the service that you need is not on the
services list.
Creating Firewall Services and Rules
You can create new firewall services and rules if you want to allow traffic that is blocked or if you
want to block specific net traffic. When you create or edit firewall rules, you should allow only
the needed services and deny all the rest to minimize security risks.
To use the Firewall Wizard, go to I want to... and click Create a firewall rule , follow the onscreen
instructions and finish the wizard.
Follow these instructions to create a new service and rule in the advaced user interface:
1. Create a new service.
a) Select the Network Services in the Advanced mode menu.
b) Define a unique name for the service in the Service Name field.
c) Enter a descriptive comment in the Description field to distinguish this service from other
services.
d) Select a protocol number for the service from the Protocol drop-down list.
If your service does not use ICMP, TCP or UDP protocol, select Numeric and type the
protocol number in the field reserved for it.
e) If your service uses the TCP or UDP protocol, define Initiator Ports the service covers.
f) If your service uses TCP or UDP protocols, define Responder Ports the service covers.
g) Click Add as a new service to add the service to the Network services list.
h) Click Save .
The new service is saved to the service list.
2. Create a new rule for the service.
54 | F-Secure Linux Security | Using the Product