Firewall's, a word synonymous with the Internet and as such, the applications we try to use over it, particularly communications. With connections to the Internet increasing every day, the world’s largest network is getting bigger and bigger.
Firewall's provide two important functions to the user: firstly, they prevent access from the public Internet to your private PC or network. Secondly, many Firewall's offer a feature called NAT (Network Address Translation) that allows you to have only one IP address on the public Internet whilst having as many as you wish on your own private intranet.
Firewall's are therefore the heart of your network security policy, and changing the policies used on these systems to allow certain ‘extra’ capabilities is often a dangerous occupation for the uninitiated, and most circumstances will result in a strong word or two from the network managers.
With the proliferation of video and voice over IP however, Firewall's have become a major obstacle. If you bypass it, using some form of proxy, then you leave yourself with a possible vulnerability to the outside world. If you try to alter the rules of operation of the firewall to allow video and audio traffic, once again, you increase your exposure to the outside.
Additionally, of course, with a NAT firewall, incoming calls can only address the public IP trying to find the private IP behind the firewall is difficult and if you provision things to allow this, such as opening “pin-holes” in the firewall, are likely to create yet another vulnerability.
