A firewall is a security feature that is designed to stop internet traffic from entering or exiting through a connection. It takes it’s name from a fireproof wall that is used, in construction, to keep out fire. In terms of Internet technology, a firewall might be a physical device, or it may be a special software that is installed on your computer. Many browsers now come with firewall technology as a means to help protect Internet surfers from hackers, malware, virus, etc.
A firewall can be used on a single computer or as a means to protect an entire network. The job of the firewall is to prevent unwanted and unauthorised Internet surfers from gaining access to either the Internet, your system or both.
How A Firewall Works:
A firewall is very effective at protecting your system or network, but their shortfall is that they are not designed to authenticate whether someone who is logged onto your system is a valid user or not. They are only designed to protect your connection to the Internet. In short, they work by sorting data and authorising Circuit and Gateway connections.
Sorting data Packets:
When a firewall is set up, special instructions are given that define data. So one of the ways that a firewall works is that it inspects each packet of data that is received or sent and once inspected it either allows the packet or it denies the packet. While this is an effective means of allowing only certain types of user defined data to flow across your Internet connection, Firewalls themselves can be difficult for the average user to set up.
Circuit and Gateway Authorisations:
What this means is that the firewall approves or denies the connect to a TCP or UDP. If the connection is approved, than the data passes through the gateway is not checked by the firewall. The firewall does not read your email or your chat conversations it simply looks at how data behaves and then grants access. With TCP, it is the connection that the firewall is concerned with because the user will have already set up a protocol for the firewall to follow when it encounters a TCP connection.
Some firewalls can act as a proxy server and mask your IP Address. When a firewall also acts as a proxy server it will allow only user identified types of applications to pass along the Internet connection. This is how companies block programs like facebook.com or youtube.com.
In short, a firewall is the best line of defence to defend your Internet connection and protect your data. They are not a complete web security measure as they can be fooled. They are also not capable of removing existing infestations of malware, spyware, or even virus from systems or networks. Every system should have a firewall of some type installed and activated.