Which of the following is the most accurate definition of a firewall?

• A. A system that blocks unauthorized or unverified access to network assets by surveying incoming and outgoing transmissions
• B. A device that takes information and scrambles it so that it is unreadable by anyone who does not have a specific code
• C. A system that authenticates users by monitoring their statistical characteristics, such as typing speed and keystroke touch
• D. None of the above

Answer: (A)

A firewall acts as a security barrier at the boundary between trusted and untrusted networks, controlling traffic by inspecting data that flows in and out and applying rules to decide what to allow or block. This description matches blocking unauthorized or unverified access to network assets by surveying incoming and outgoing transmissions. Encryption (the idea of scrambling data) hides content but doesn’t by itself control access to network resources, and biometric-style user authentication isn’t what a firewall does. So this option best captures the firewall’s purpose.