Contributed by Gary Palmer
<gpalmer@FreeBSD.ORG> and Alex Nash
<alex@freebsd.org>.
Firewalls are an area of increasing interest for people who are connected to the Internet, and are even finding applications on private networks to provide enhanced security. This section will hopefully explain what firewalls are, how to use them, and how to use the facilities provided in the FreeBSD kernel to implement them.
Note: People often think that having a firewall between your companies internal network and the ``Big Bad Internet'' will solve all your security problems. It may help, but a poorly setup firewall system is more of a security risk than not having one at all. A firewall can only add another layer of security to your systems, but they will not be able to stop a really determined cracker from penetrating your internal network. If you let internal security lapse because you believe your firewall to be impenetrable, you have just made the crackers job that bit easier.