A firewall is means of blocking access to a computer and and any private data contained on it, while connected to an external network such as the Net.
When you are online, your computer uses ports to communicate with the Web. There are over 65,000 discrete ports (65,536 to be exact), each used for different types of data transmission. For example:
Unused ports are often used to gain entry to your computer without your knowledge. Firewalls monitor the ports on your PC and alert you to any unauthorised attempts to transmit or receive data.
How open to attack is your system? Check now... Tools provided by the Gibson Research Corporation.