What does a firewall do?

A firewall is primarily designed to act as a barrier between internal networks and external networks, serving the purpose of monitoring and controlling incoming and outgoing network traffic based on predetermined security rules. This combination of hardware and software creates a protective layer that helps prevent unauthorized access, cyberattacks, and potential data breaches. By segregating networks, firewalls contribute to the overall security posture of an organization, ensuring that sensitive information remains protected from external threats.

The other options touch on important aspects of cybersecurity but do not accurately define the function of a firewall. For example, while encryption and keys are important for securing data (as mentioned in the first option), they do not characterize the primary role of a firewall. Similarly, while a multilayered approach (mentioned in the second option) and regular patching (from the third option) are essential for effective cybersecurity strategies, they represent different security practices rather than the specific function of a firewall. Thus, the correct answer encapsulates the essential role of firewalls in network security.