How are firewalls are built?

Firewalls are built using a combination of hardware and software components designed to monitor and control incoming and outgoing network traffic. They establish a barrier between trusted internal networks and untrusted external networks by enforcing predetermined security rules. Typically, firewalls analyze data packets, filtering them based on criteria such as IP addresses, port numbers, and protocols. Modern firewalls may also incorporate advanced features like intrusion detection systems, VPN support, and application-layer filtering to enhance security.