What Is a Firewall?
A firewall is a type of network security system that helps protect your network from external threats by controlling incoming and outgoing network traffic. A firewall can be either software-based or hardware-based. A hardware firewall is typically a router, which is a physical device that blocks traffic from accessing the internal network. A software firewall works similarly, but is installed on your device. For instance, the Windows Firewall comes with operating systems Windows XP SP2 and later.