Firewalls are a mainstay of network security. At its core, the firewall acts as a barrier between a trusted internal network and untrusted external networks, such as the Internet. Its primary function is to monitor and control incoming and outgoing network traffic based on predetermined security rules. Think of the firewall as a gatekeeper scrutinizing every packet of data that attempts to pass through. Let’s take a look at the different types of firewalls and some of their key functions.