The term “fire wall” originally was coined from a fireproof wall intended to prevent the spread of fire from one room or area of a building to another. The Internet is a volatile and unsafe environment when viewed from a computer-security perspective, therefore “firewall” is an excellent metaphor for network security. In computer networking, the term firewall is not merely descriptive of a general idea. It has come to mean some very precise things. The most important aspect of a firewall is that it is at the entry point of the networked system it protects. In the case of Packet Filtering, it is at the lowest level, or “layer” in the hierarchy (stack) of network processes, called the Network Layer or the Internet Layer. This means essentially that the firewall is the first program or process that receives and handles incoming network traffic, and it is the last to handle outgoing traffic. The logic is there for very simple: a firewall must be positioned to control all traffic to and from any given network. In cases of large companies that use lots of network resources and browse the Web while at work, there is what is known as the term firewall. Many times we hear people talk of things like, they could not use that sites because they wouldn’t get through the firewall. If you have a fast Internet connection into your work place, you may have found yourself hearing about firewalls for your home network as well. It turns out that a small home network has many of the same security issues that a large corporate network does. You can use a simple firewall windows built in to protect your home network and family from offensive Web sites and potential hackers. In reality, a firewall is a barrier to keep destructive elements away from your computer and other network devices. In fact, that’s most probably why it is called a firewall. Its job is similar to a physical or firewall that keeps a fire from spreading from one area to the next. A firewall is simply a program or hardware device that filters the information coming through the Internet connection into your private network or computer system. If an incoming packet of information is flagged by the filters, it is not allowed through. Let’s say that you work at a company with a hundred or so employees, the company will therefore have a hundred or so computers that all have network cards connecting them together. In addition, the company will have one or more connections to the Internet through a public internet. Without a firewall in place, all of those hundreds of computers are directly accessible to anyone on the Internet. A person who knows what he or she is doing can probe those computers, try to make FTP connections to them, try to make telnet connections to them and so on. If one employee makes a mistake and leaves a security hole, hackers can get to the machine and exploit the hole or vulnerability. With a firewalls in place, the internet landscape is much defined. An organisation can deploy a firewall at any connection to the Internet. The firewall can implement security rules. Out of the hundreds of computers in an organisation, only one can act as the front office, permitted to receive public internet traffic connections and only that one computer can link the organisation, preventing the others from direct link outside. (to be Cont’d) eddie@afrowebs.com
