Security

[riser]

Rules are required for any software (games, skype, etc.) that needs to communicate external machines (network/internet).

Each application will have ports that it uses to listen on.  The port(s) may be TCP or UDP.

Using a firewall requires that you understand what you use and what it needs.

[Coastie]

Thanks. Since I do not think I have any need to communicate with any external machines, it is OK that do not understand what I use and what it needs.

[davidrom42]

Use the software of firewall. A software based firewall is better and more effective.

Linux Firewall