A network firewall protects a computer network from unauthorized access. It might be a hardware device, software program, or a combination of the two.
Network firewalls guard an internal computer network against malicious access from the outside, such as malware-infested websites or vulnerable open network ports. You can find them anywhere a network is used, like at home, school, business, or even an intranet.
A network firewall may also be configured to limit access to the outside from internal users, as in the case of parental controls or workplace locks, both of which commonly prevent access to gambling and adult websites, among many other content types.
How a Firewall Works:
When a firewall is used at its full potential, it constantly monitors all incoming and outgoing traffic. What makes a firewall different from just a traffic analyzer is that it can also be set up to block certain things.
A firewall might disable particular applications from accessing the network, block URLs from loading, and prevent traffic through certain network ports.
Some firewalls can even be used in mode where they block everything until you explicitly allow each single access. This is one way to block everything on a network so that you can manually set up safeguards against network-related threats.