What is Firewalls?

Understanding Firewalls

Devices that enforce administrative security policies by filtering incoming traffic based on a set of rules. Firewalls are network security devices or software that monitor and control incoming and outgoing network traffic based on predetermined security rules. They establish a barrier between trusted internal networks and untrusted external networks, filtering traffic based on parameters like source destination addresses, ports, and protocols. Firewall implementation is mandated by standards like PCI DSS, ISO 27001, and NIST SP 800-41. Organizations implement firewall security through next-generation firewalls, web application firewalls, host-based firewalls, network segmentation, and defense-in-depth strategies. For example, an enterprise might deploy perimeter firewalls at internet connection points, internal firewalls between network segments, web application firewalls for public-facing applications, and host-based firewalls on individual systems. Related terms: Network security, Packet filtering, Stateful inspection, Next-generation firewall, Web application firewall, Network segmentation, Defense in depth.