Which of the following is the best advice to protect your private network from an untrusted public network?

To effectively protect a private network from the vulnerabilities of an untrusted public network, using a firewall is a critical security measure. A firewall acts as a barrier between a trusted internal network and untrusted external networks, controlling the traffic that is allowed in or out based on predetermined security rules. It helps to prevent unauthorized access, malware, and various types of cyber attacks by filtering incoming and outgoing data packets.

While other options like a VPN (Virtual Private Network) provide encryption and a secure tunnel for data transmission, which is beneficial for protecting data privacy over untrusted networks, the firewall serves as the first line of defense by actively managing and controlling network traffic. This proactive approach reduces the risk of external threats penetrating the private network.

In contrast, a gateway typically facilitates communication between different networks and may not inherently provide the protective measures that a firewall does. A proxy server can also offer privacy and anonymity but may not provide the comprehensive security capabilities needed to shield an entire private network effectively. Thus, the choice of a firewall as the best advice underscores its essential role in safeguarding the internal network against distinct threats from untrusted environments.