Firewall

A firewall is a network security device (hardware or software) that monitors and controls incoming and outgoing network traffic based on predetermined security rules. Think of it as a security guard at the entrance to your network — it checks every connection attempt and either allows or blocks it based on your policies.

Modern firewalls go beyond simple port-based filtering. Next-generation firewalls (NGFWs) can inspect the content of network traffic, identify applications, detect malware, and prevent intrusions — all at the network perimeter. Properly configured firewalls are a foundational defense for any network.