A firewall is a network security device that monitors and controls incoming and outgoing traffic based on predefined security rules. It typically operates at the network level, forming a barrier between a trusted internal network and untrusted external networks (like the internet). Firewalls are perimeter-based and often focus on allowing or blocking traffic based on IP addresses, ports, or protocols. ZTNA, on the other hand, is a more advanced security model that operates on the principle of Zero Trust, requiring continuous identity verification before granting access to specific applications or resources. ZTNA does not rely on predefined network perimeters; instead, it works on an identity-based access model and ensures that access is granted only after verifying multiple factors such as user identity, device health, and contextual data. While firewalls are effective at securing the network perimeter, ZTNA focuses on securing access to applications and data, regardless of the network location.