What is the main function of firewalls?

• A. To monitor and control incoming and outgoing network traffic based on security rules
• B. To monitor user accounts
• C. To provide DNS resolution
• D. To encrypt data in transit

Answer: (A)

Firewalls enforce security policy by monitoring and filtering network traffic between networks or segments. They examine both directions of traffic and apply configurable rules to decide what to allow, block, or log. This helps prevent unauthorized access, restricts harmful traffic, and supports network segmentation by enforcing who can talk to whom, over which ports and protocols, and under what conditions. Stateful firewalls remember ongoing connections to allow legitimate return traffic, and many also offer features like logging, VPN support, or basic application awareness. They don’t monitor user accounts, provide DNS resolution, or inherently encrypt data in transit (though they may work alongside encryption or VPNs and can perform certain inspection tasks).