Firewall

A Firewall is a security system (either software of a hardware) that protects the computer from outer threats. It controls all the incoming and outgoing network traffic, analyzes it, and decides whether it should be allowed to go through. All this is done based on previously determined set of rules. The firewall functions like a bridge that divides the internal network of the computer from the outer network, like the Internet.

Most computers have software-based firewalls that protect the computers from threats that usually come from the Internet.