Free firewalls have become very common and represent an excellent alternative to commercial firewall packages. Most of these firewalls run under some form of Linux, FreeBSD, or OpenBSD. Many of these free firewalls are front-ends for lower-level firewall packages such as pf, iptables, and ipchains.

Firewall Builder is a firewall configuration and management GUI that supports configuring a wide range of firewalls from a single application. Supported firewalls include Linux iptables, BSD pf, Cisco ASA/PIX, Cisco router access lists and many more.

With the prevalence of "black box" appliance firewalls available for $50 or less, one might wonder why you would look for a do-it-yourself solution. Linksys and D-Link, among other vendors, create simple and easy to configure firewall solutions for cheap.

The UFW has a GUI front end that you can add to it to provide an “easier” method of working with the firewall. You will see that it will be installed and available using System/Adminstration/Firewall administration. The interface is set up for several different options.

On Fedora 18, the new firewall application is called FirewallD. It has its own command-line and graphical utility, but the graphical firewall tool installed belongs to the old firewall application which it replaced.

Debian Administration has an article up about the usefulness of firewalls. Are they really necessary? If you consider a firewall as just a non-stateful, layer-3 packet filter, then I would agree they are not very useful. However, modern firewalls can do all sorts of useful filtering that can protect a public application from compromise

Most firewall systems contain a Web-based component that allows you to configure the firewall. This holds true for most entry-level firewall systems (Linksys, D-Link, etc.) and also open source firewall systems such as pfSense. These systems tend to provide ways to access the Web interface remotely via the Internet; however, this should not be considered secure at all.

This article continues the series of articles on Fireall Builder, a graphical firewall configuration and management tool that supports many Open Source firewall platforms as well as Cisco IOS access lists and Cisco ASA (PIX).

Firewalld is Fedora’s way to provide dynamic firewall properties in Linux. Thus way changes in the firewall configuration are applied immediately, without the need to restart. Additionally, firewalld supports D-BUS and zone concepts.

Firewalld replaced Fedora’s old firewall mechanism with Fedora 18.