An expert once said, using Linux without a firewall in place is akin to having unprotected sex. You never know when your system will be compromised. That doesn't mean that Linux is devoid of any firewall software. For one you have the ubiquitous iptables which is installed by default on all Linux machines (albeit with an open policy). So to make your machine secure, some amount of work has to be done. I had described the basics of configuring iptables in previous articles namely - "iptables - The poor man's robust firewall for Linux" (Click here) and "Designing a firewall using Iptables for the Home User" (Click here).
But there are other firewalls too available for Linux and one such firewall software is IPCop. What is unique about IPCop is that it acts as a standalone solution tailor made for the enterprise networks. What is more, it provides much more features than the basic iptables/ ipchains firewall implementation and can easily be extended to include other features through add-ons.
Joseph Guarino has written a two part series which simplifies the installation and configuration of IPCop firewall software which should be quite informative for any one in the business of Linux security. In the first part of the series, he walks one through the installation of the software and in the second part, he dwells on the more advanced topics like setting up a firewall using IPCop for mail and web servers, installing a very useful add-on called copfilter to enhance the firewall setup and more. The interesting thing is, once you have installed the firewall software, the configuration can be done using a easily accessible web interface which endows this software a great degree of userfriendliness.