A firewall is a security measure that protects a computer or a computer network from unauthorized access. A firewall can be software, hardware, or a combination of both. A good firewall will prevent hackers from accessing a computer. It will keep personal information safe. Firewalls don\'t prevent virus attack but in some circumstances they can stop viruses from sending information from an infected computer.

Having a firewall on a computer with a dial-up Internet connection is good but not a necessity. (If you use a regular telephone line and you click on an icon on your computer desktop to initiate your Internet connection, you have a dial-up connection.) However, unlike dial-up connections, both DSL and cable connections are always on, shared connections. It is easier for an intruder to break into your computer if you are using one of these connections. So it is essential to have a firewall on a computer that uses DSL or cable to connect to the Internet.