What is the function of a firewall in network security?

• A. To monitor traffic at the network edge and log events.
• B. To control traffic between networks by enforcing security rules.
• C. To encrypt all network traffic end-to-end.
• D. To provide user authentication for remote access.

Answer: (B)

Firewalls enforce security policies by controlling what traffic is allowed to pass between networks. They sit at the boundary between a trusted network and an untrusted one and apply defined rules to each connection, often based on source and destination IPs, ports, and protocols, and in stateful systems, the state of the connection. This rule-based filtering blocks unauthorized access and limits harmful traffic, helping protect internal systems while still permitting legitimate communication. Logging or monitoring can be features, but the core function is enforcing policy to control flow between networks. Encryption of all traffic end-to-end is handled by VPNs or encryption protocols, and user authentication for remote access is handled by authentication services; those are separate from the firewall’s primary role.