What is a Firewall?
There are two types of firewall, a dedicated firewall and a personal firewall. Dedicated firewalls are used by companies and organisations on a large scale therefore I will concentrate on personal firewalls.
A Personal firewall is a piece of software that studies all data being transferred to and from the computer it is installed on. It then allows you to accept, deny or restrict access to and from the computer. If for instance another program is trying to access the internet without asking you, the firewall will ask if you want to allow it access or block it depending on the rules you specify in the firewall. A firewall helps root out suspicious internet access by unauthorised programs. Windows XP and Vista both have firewalls installed with the operating system. Make sure they are turned on to protect your pc.