What is the initial layer of protection to prevent unauthorized access to a facility's information network?

The correct choice is a firewall because it acts as the primary barrier between an internal network and external threats, helping to monitor and control incoming and outgoing network traffic. A firewall establishes a set of rules that determine what data can enter or exit the network, effectively blocking unauthorized access and potential attacks. This makes it essential in safeguarding sensitive information housed within a facility's network.

While other options like antivirus software and encryption provide additional layers of security, they do not serve as the first line of defense in managing access to the network itself. Antivirus software primarily detects and removes malware after it has infiltrated a system, and encryption protects data in transit and at rest, but neither directly controls access to the network. A network password is important for securing user accounts and devices, but without a firewall, the network could still be exposed to broader threats. Thus, the firewall is fundamental in establishing a secure perimeter around the information network.