Welcome to the jargon buster, where we aim to cut through and explain some of the terminology used in the online world. The jargon buster is in its infancy at this stage - if there are any terms or abbreviations you would like added to this page, please let us know.
Firewall
A firewall is a hardware or software device that sits between a computer/network and the public Internet. By providing an intermediary stage between internal computers and the external Internet, firewalls are used to filter both incoming and outgoing traffic.
The way in which the firewall chooses to filter traffic can usually be configured by the administrator. Most good firewalls will allow rules to be defined by the administrator that define exactly what traffic should be allowed (or disallowed) into a network.
For example, a firewall can be configured to reject traffic on particular computer port numbers, block certain services from accessing the Internet (such as Instant Messaging tools), prevent traffic from entering a network unless it was explicitly requested, and filter outgoing traffic.
The use of a firewall is only a small yet important factor in securing your computer. Windows XP contains a built in firewall that was automatically turned on during the Windows XP Service Pack 2 update (see Windows® updates). An example of a good free firewall is available here.
As well as implementing a good firewall, you should also regularly run up to date antivirus software. Please take the time to update your antivirus software, as old definition files may render your software useless in today's virus infested Internet.