Definition

What is Firewall?

A network security control that monitors and filters traffic between networks based on predefined security rules. Traditional firewalls operate at the network and transport layers, enforcing rules by IP address and port; next-generation firewalls (NGFW) add application-layer inspection, user identity awareness, and threat intelligence integration. Firewalls are a necessary but insufficient control — they provide no protection against application-layer attacks on permitted traffic.

Related terms

Web Application Firewall (WAF) →

A security control that monitors, filters, and blocks HTTP/HTTPS traffic between clients and a web application based on rule sets designed to detect common attack patterns.

Intrusion Detection System (IDS) →

A monitoring system that analyzes network traffic or host activity for signs of malicious behavior and generates alerts when suspicious patterns are detected.

Defense in Depth →

A security strategy that layers multiple independent controls so that the failure of any single control does not result in a complete breach.

Zero Trust →

A security model built on the principle that no user, device, or network segment should be implicitly trusted — even those already inside a traditional network perimeter.

Put this into practice

AI penetration testing for web applications →

See how Penetrify's autonomous AI agents find and validate this class of security issue in your application.