What is the function of a firewall in a network?

• A. To route traffic between networks.
• B. To monitor wireless signal strength.
• C. To log all traffic for auditing.
• D. To filter traffic between networks based on security rules, protecting against unauthorized access and threats.

Answer: (D)

Firewalls filter and control traffic at network boundaries by applying security rules to what is allowed or blocked. They inspect data moving between networks and decide, based on configured policies, which packets can pass and which should be blocked, protecting against unauthorized access and threats. That direct role—filtering traffic between networks according to security rules—is what this item is describing. Other choices describe tasks outside the firewall’s main job: routing is done by routers, monitoring wireless signal strength is about signal performance, and logging can happen as a feature but isn’t the primary function of a firewall.