What is the primary function of a firewall?

• A. Monitor and control incoming and outgoing network traffic to block threats
• B. Encrypt all traffic by default
• C. Increase bandwidth
• D. Provide domain name resolution

Answer: (A)

Firewalls act as the gatekeeper between networks, monitoring and controlling incoming and outgoing traffic based on predefined security rules to block threats. This dual role of inspection and enforcement is why it’s the best description: the firewall decides which data can pass and which should be blocked, helping prevent unauthorized access, malware, and other dangers from crossing the boundary. It can use rules tied to IP addresses, ports, protocols, and even application characteristics (in advanced setups) and may track connection states to ensure only legitimate return traffic is allowed. The other options describe functions not inherent to firewalls: encrypting all traffic by default is the job of encryption mechanisms or VPNs, not a firewall; increasing bandwidth isn’t a firewall function; and providing domain name resolution is the domain of DNS services.