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.

The growth of the internet has brought in to the introduction of many firewall applications, each one having different features. Windows firewall is an application offered for free with the purchase of Windows OS.

Since the function of the firewall is based on the set of rules, it can often become worthless, if not configured properly. Optimized analysis has to be done on a computer followed by changes in the settings 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 function is a proxy based application layer firewall. This detects the applications and protocols sneaking in, through the non standard ports. Harmful and abused protocols are also blocked.

Application layer-firewalls works on the application level of the TCP/IP stack and may intercept all packets traveling to or from an application. They block other packets. These application firewalls will prevent all unwanted outside traffic from reaching protected machines. On inspecting all packets for improper content, firewalls can prevent outright the spread of networked worms and most harmful Trojans.