FirewallThe main purpose of firewall software is to block unauthorised access while still allowing authorised communications. Basically a firewall checks the incoming transmissions against a set of rules and if the incoming transmission does not meet the standards of those rules then the transmission is denied. Certain rules for a firewall can be changed by the user, for example the user can select whether they want certain ports to be open or closed and can also set a list of web addresses that the firewall should always allow data from. Firewalls are often included with most anti-virus software; however with certain packages it is clear that the brand providers have put more effort into developing the anti-virus more than the firewall side.