What network security measure examines and remediates foreign hosts attempting to access a network?

The correct answer is Network Access Control (NAC) because it is specifically designed to enforce security policies on devices attempting to access a network. NAC solutions validate the security posture of each device before granting it access, ensuring that only compliant devices are allowed onto the network. This technology helps protect the network from unauthorized or potentially harmful foreign hosts, by checking factors such as the device’s operating system, the presence of antivirus software, and whether the software is up-to-date.

In contrast, firewalls primarily focus on preventing unauthorized access or blocking certain types of traffic based on pre-defined rules, rather than specifically examining the compliance of devices. An Intrusion Detection System (IDS) monitors network traffic for suspicious activity and alerts on potential intrusions but does not actively control device access to the network. A Virtual Private Network (VPN) primarily provides secure remote access to networks over the internet but does not assess or remediate the security status of connecting devices. Thus, NAC encompasses the broad range of functions needed to evaluate and control access by foreign hosts seeking entry into the network, making it the most fitting choice in this context.