A firewall is a security system that typically sits between you as a computer user and the internet. It monitors and controls traffic to and from the internet based on a set of security rules. Think of it like the bouncer at a night club. The bouncer looks at everyone in line and decides who can come in using a set of criteria. Imagine that he can tell, just by looking at you, who you are, where you’re from, and whether you’re going to cause trouble. If you’re on the guest list, he might send you straight to the VIP area. But if you look like a troublemaker or have a bad reputation, there’s no way he’ll let you in. Firewalls do the same thing with files and communications trying to get to your computer. They let in the good files and keep out the bad. They can also help control which applications on your computer are able to communicate with the internet, especially on their own.
Firewalls can be hardware- or software-based, or some combination of the two. Most home users are more familiar with software firewalls. Many operating systems, such as Windows® OS and Linux include basic, built-in software-based firewalls. Antivirus and other internet security products may also include software firewalls. Hardware firewalls are typically used in businesses and large corporations. These are often physical devices that are placed between the router and the internet connection. Since these are external devices, they don’t use up any computing power on the devices that use it to connect to the internet, but they can be difficult or time-consuming to maintain and configure.