The term firewall was first used when describing insulated, sturdy metal wall designed to keep car passengers safe from the heat of an engine. Firewalls in a computer are designed to keep all unsolicited traffic out of your computer.

 

Imagine you are the owner of a fancy invite-only nightclub, and you don't want any undesirable patrons in your establishment. To keep out the people not “on the list,” you hire a doorman. In the case of your computer, you install a firewall keep out the Internet traffic you don’t want.

For example, if you want to use the search engine Google, you would type www.google.com. The firewall in your computer keeps the address(es) of the Web sites you want to view, in this case www.google.com. When the response comes back from Google, your firewall lets the data pass through. But if a response comes back to your machine with an unknown address, the firewall doesn't let any data in.

 

Internet Explorer uses the firewall built into Windows, called Windows Firewall, which provides a good level of protection. There are also many different programs available, some which are free and some which you need to pay a monthly or yearly fee to use.