A firewall is a piece of software or a hardware device that operates between your computer and the Internet. The firewall helps screen out hackers, viruses, and worms that try to reach your computer over the Internet.
A firewall monitors traffic patterns to and from your computer. When you computer communicates across the Internet, normally an application on your computer 'requests' information from the Internet. The firewall makes sure that this request is an authorised request, and that the response from the Internet is linked to the original request from your computer. If the firewall sees an incoming request from the Internet to your computer that has not been initiated from your computer, depending on the firewall settings it will block the access attempt. Many hackers attempt to look for open 'ports' on your computer that run services needed by the computer. Often these services have vulnerabilities that hackers can exploit if the services are left open. This is where the firewall is of most benefit.
Firewalls often perform Network Address Translation (NAT) which is an essential service to run on computers connecting to the Internet. NAT effectively hides your IP address so that hackers on the Internet cannot easily find you through their scanning techniques.
Do I need to use a firewall on campus?
If your computer is connected on campus to the University network then you are already largely protected from the Internet by the University's firewall. However, virus outbreaks can still occur within the University network and hackers can operate inside the University network. This means that while you are largely protected on campus, a personal firewall should also be considered.
Do I need to use a firewall at home or while travelling?
Yes if you are a home user, or you take your work laptop home or travel with your laptop and connect to the Internet through your own ISP or via the University modems. In these cases using a firewall is essential and is one of the most effective and important steps you can take to help protect your computer when on the Internet.
Firewall information for Windows XP users
Microsoft has a built in firewall with Windows XP and has a comprehensive guide here: Microsoft Firewall Guide
Firewall information for non Windows XP users
If you are on campus your computer is largely protected from the University's firewall. However, home users and staff and students who take laptops home should use a firewall. Information on free and commercial firewalls is here: The Firewall Guide
Updated: 23 April 2012