Computer firewall is an OS based software designed to control the access to unauthorized content on a network or a computer system. It works with predefined set of rules, according to which it decides whether to block or allow access.

Windows firewall is the firewall application used by many windows users. It acts quickly to the attacking Trojans and blocks the access to those networks. Access to the blocked networks is possible only when the setting of the application is changed.

This firewall technology was found in the 1980s, when internet itself had not reached the people widely. Routers were used to separate network accessibility and the demand for network security was not necessary.

Day by day the use of internet access is gradually increasing. It leads to develop more applications for internet security. By this firewall was lunched for security administration. Windows firewall is available with the purchase of windows OS.

Firewall functions under certain set of rules and instructions. If it is not working it will become worthless. Optimized analysis makes changes in settings of security administration. All these are working for complete protection.

The functions of a Computer firewall are classified into three generation sets. All three functions are necessary to provide online and offline support. These generation sets control the installation, copying and sharing of a file.

The first function is called a “packet filter”, which stays focused with the data units transferred from the network. The second one, called as “stateful filter”, which records the list of connections passed and uses this to determine the state of the packets.

The third generation firewall also known as proxy-based firewall and also called as application-layer firewall. Its main function is to detect unwanted harmful threats and abused protocols. After detection it will automatically blocks those unwanted threats.

Application layer-firewalls works on the application level of the TCP/IP stack. And it will intercept all packets traveling to or from an application. Firewalls are used to search unwanted outside traffic from computer. Firewalls will prevent outright the spread of worms and Trojans.