How Firewalls Work

To understand the working of  firewalls is not enough difficult as many people think. The working of firewall is depend on some steps.

• When you start communicating to other computers or device over the Internet, your computers follow the TCP 3-way handshaking process, in general your computer send a request to the network for the sake of communication.

• If you have a firewall on your computer, then first firewall check that request and compare it with different types of rules and regulation of the firewall.
• Firewall also checking the source of networking and web-hosting and than firewall makes decision either file to be transfer or deny.
• The rules and regulation of the firewall set by the administrator of the computer or a network.
• Firewall also work on the authentication process for the safe communication, if some thing is missing in the authentication it will block the whole communication.

Firewalls can be divided by their configuration techniques or application.

Network-Level Firewalls or Packet filtering

Network layer firewalls, also called packet filters. It generally make their decisions based on the source address, destination address and ports in individual IP packets. A simple router is the traditional network layer firewall.

Application-layer Firewalls

Application-level firewalls looking more deeply into the application that communicate to the internet, it restrict the rules for the application like TCP,FTP,Telnet or UDP etc.
Application-level filtering may include protection against spam and viruses as well, and be able to block undesirable Web sites based on content rather than just their IP address.