A ‘firewall’ secures your computer system by isolating it from the Internet. Its purpose is to inspect and control all data running between your computer and the Internet. It handles this in such a way that potentially dangerous occurrences are detected and dealt with. If necessary these and other occurrences are logged.

What the firewall considers as a potentially dangerous occurrence is determined by the security settings of your firewall software.

Without a firewall, whenever your computer is connected to the Internet your computer is open to attack! The threat runs from the curious browser to well-organised and technically knowledgeable intruders who can gain access to your files and interfere with the use of your computer.

A firewall works just like the security guard in an office building. He or she checks the identity and purpose of everyone who attempts to enter, logs them in when they arrive and logs them out when they leave. The guard denies access to anyone who doesn’t have permission to enter the building.