Firewalls can be a software program on your computer or an external box, like a broadband router. Both will protect your system. Each one has advantages and disadvantages.

A hardware firewall never lets anyone even get to your computer before it blocks hackers. In addition, it isn't vulnerable to the weaknesses of your computer's operating system. It usually runs a more secure and simple operating system, so it's harder for hackers to break in.

A software firewall can block outgoing connections from spyware and other programs already on your computer. However, if your operating system is compromised, your firewall may be, too. In addition, by the time hacker reaches your firewall, they've already reached your computer. While they still probably won't get in, a separate device can make it harder to jump into your system.

If you run a wireless router, it's a good idea to also run a software firewall on your computer. While the router will protect you from Internet threats, the software firewall will protect you from those people within range of your wireless connection.