What is Firewall? 

What is Firewall?

If you have been using the Internet for any length of time, and especially if you work at a larger company and browse the Web while you are at work, you have probably heard the term Firewall used. For example, you often hear people in companies say things like, "I can't use that site because they won't let it through the firewall."
If you have a fast Internet connection into your home, 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 firewall to protect your home network and family from offensive Web sites and potential hackers.
Basically, a firewall is a barrier to keep destructive forces away from your property. In fact, that's why it???s called a firewall. Its job is similar to a physical firewall that keeps a fire from spreading from one area to the next.
A security device built into many Internet servers. Firewalls help prevent unauthorized activity on the server. Programs that charge a fee generally have a firewall that prevents access unless you enter an authorized username and password. On networks, firewalls are used to prevent Internet users from accessing files other than public internet material. Firewall also refers to a class of software that can be installed on computers that use cable modems or DSL. These communication systems are "always on" so it is possible that someone else on the Internet can maliciously access your computer.
Therefore, firewall is a device that interfaces the network to the outside world and shields the network from unauthorized users. The firewall does this by blocking certain types of traffic. For example, some firewalls permit only electronic mail traffic to enter the network from elsewhere. This helps protect the network against attacks made to other network resources, such as sensitive files, databases, and applications.