According to K Schulz, firewalls are like so many other things in computers; they are following an evolutionary path away from customized software solutions to "plug-and-go" black box appliances.

This trend is nothing new. We've seen this happen in other special-purpose devices, such as the common router. Routers started as network daemons in Unix boxes and evolved into the Cisco, Bay and Ascend routing and switching products that we rely on and use every day.  Firewalls are no different. In the past, if you wanted to install a firewall you had to purchase the software, sometimes the underlying operating system, and also a computer on which to run it all. It was no surprise that just to get a single firewall in place, it would run into the tens of thousands of dollars. What if you needed to protect five or more entry points into your network, or just wanted to place a firewall between workgroups? Cost simply got in the way.  And cost wasn't even the biggest concern if you weren't fully confident that your setup was providing adequate security.

Some firewall appliances are specifically designed to do one thing-and they do it very well. Inside, you will find both application and packet filters or some form of stateful inspection engine. Some are based on a sealed-up PC, complete with hard drives and file and operating systems. Others are solid-state embedded systems that have no moving parts and know only one task.  Many of these devices now offer far more than just firewall protection. 

Also available for most are virtual private network (VPN) modules to create secure tunnels from firewall to firewall, URL and keyword content filtering to block access to nonproductive areas of the Internet, and, of course, network address translation (NAT) to handle your TCP/IP addresses on your network. Others can act as a Web caching proxy; still others provide SMTP mail server functionality.  Please click on the links below for more information.

Fort Knox Policy Router

Sonic Wall and Interpol

Checkpoint