This little tool allows you to set up a
basic firewall on your machine. It filters connection attempts
made from the outside, and blocks unauthorized ones. It's a good
idea to run it just after installing your
machine and before connecting to the
Internet, therefore minimizing the risks of your machine being
cracked.
If checked, uncheck the Everything (no firewall) box, and then check the boxes corresponding to the services you wish to make available to the outside world. If you wish to authorize a service which isn't listed here, click on to manually enter the port numbers to open.
Not checking a service in this list won't disallow you from connecting to it. It will only prevent people from the Internet to connect to that service on your machine. If you don't plan on hosting any service on your machine (common case for a desktop machine) just leave all boxes unchecked.
On the other hand if you wish to disable the firewall and leave all services accessible from the outside, check Everything (no firewall), but please bear in mind that this is very insecure, and therefore not recommended.
Then clicking on will bring you to the next step, which consists of selecting the network interface connected to the Internet.
Refer to the examples to determine the name of your interface to the Internet. If you're unsure, you can check the system network configuration (see Section 1.3, “Reconfigure Interfaces”). You can finally click to install the required packages, activate the firewall and enjoy your secure Internet connection.