10.5.4.1. What is a firewall?
In the previous section we already mentioned firewall
capabilities in Linux. While firewall administration is one of the
tasks of your network admin, you should know a couple of things
Firewall is a vague term that can mean anything that
acts as a protective barrier between us and the outside world,
generally the Internet. A firewall can be a dedicated system or a
specific application that provides this functionality. Or it can be
a combination of components, including various combinations of
hardware and software. Firewalls are built from "rules" that are used to define what is allowed to
enter and/or exit a given system or network.
After disabling unnecessary services, we now want to restrict
accepted services as to allow only the minimum required
connections. A fine example is working from home: only the specific
connection between your office and your home should be allowed,
connections from other machines on the Internet should be