Firewall - Introduction:

It is a combination of hardware and software that provides a security system, usually to prevent unauthorized access from outerside to an internal network that is intranet. A firewall prevents direct communication between network and external computers by routing communication through a proxy server outside of the network. The proxy server determines whether it is safe to let a file pass through to the network. A firewall is also called a security-edge gateway. Someone on the Internet or a network try to connect to your computer through internet connection , in this attempt is called an "unsolicited request." 

FireWall Description and application :  Fire helps to keep your computer more secure. For example Yo are working in office . it Restricts information that comes to your computer from other computers, That is to prevent unwanted patches,virus from others to your computer . It giving you more control over the data on your computer.

For Example

1. When your computer gets an "unsolicited request", Windows Firewall blocks the connection. 2. If you run a program like an instant messaging program or game that needs to receive information from the Internet or a Group of systems (network), 3. The firewall asks if you want to block or unblock (means allow) the connection.  4. If you choose to unblock the connection, Windows Firewall creates an exception so that the firewall won't bother you  When that program needs to receive information in the future.  an example , "if you are exchanging instant messages with someone who wants to send you a file (a photo, for example),  Windows Firewall will ask you if you want to unblock the connection and allow the photo to reach your computer. (OR) if you want to play a multiplayer network game with friends over the Internet, you can add the game as an exception  so that the firewall will allow the game information to reach your computer. Although you can turn off Windows Firewall  for specific Internet and network connections, doing this increases the risk that the security of your computer might be compromised "  How Turn On windows Firewall:   1. in windows XP right click the "My network place tab" and select "properties" 2. Also Right click the "lacal area connection" and select "properties"

In this "Advanced" tab and choose windows firewall "settings"

In this the General tab, click one of the below :

  1.  On (recommended).  You can also select the Don't allow check box. When this check box is selected, the firewall blocks all unsolicited requests to connect to your computer, including requests to programs or services selected on the Exceptions tab. Use this setting when you need maximum protection for your computer, such as when you connect to a public network in a hotel or airport, or when a dangerous virus or worm is spreading over the Internet.

2.   Off (not recommended).

       Turning off Windows Firewall might make your computer (and your network, if you have one) more to damage from viruses or unknown intruders