Firewalls


 * __Firewalls__**

Firewalls are used to prevent or allow network transmissions in computer systems, and are generally used to protect opertating systems when connected to the internet. Most home computer operating systems in the modern day come with a built in firewall, this means that even those who are oblivious to what a firewall is and what it does, are still protected from hackers and viruses/trojans/etc. Better firewalls can be downloaded/bought if you feel that your current firewall isn't good enough, or if you keep getting viruses which will increase the network security of your system.

You can also find firewalls in routers and homehubs that you may use to allow your family to all connect to the internet simultaneously. This second firewall adds further protection to the security of computer systems connected to the internet and allows computers with non-upgraded firewalls to have better protection. However running a computer with two or more firewalls installed on the hard disk can also prove to be detrimental to your system.

__**History**__ The first generation of firewalls were called 'Packet Filters'. Packet filters inspected the packets of data sent to the system and if the packets matched a set of predefined rules then they would be dicarded or rejected by the firewall so-as to block out unwanted data.
 * First Generation**

The second generation firewalls are known as 'Stateful Filters'. The firewalls asses the location of the packets, as well as doing the same as a first generation firewall, which allows the firewall to tell if the packets come from a new connection, the same connection or if the packet is invalid.
 * Second Generation**

Application Layer Filtering is the name given to the third generation of firewall. The application layer filter does the same as first and second generation firewalls, however the application layer filter can also block data on the basis of content and can 'understand' certain aplications and protocals. Because of it's sophistication, the application layer filter can also block indevidual words and numbers. This is by far the most protective of the three.
 * Third Generation**