Which of the following should be used to ensure that a device is inaccessible to a network-connected resource?

Disabling unused services can reduce the attack surface of a device by preventing potential vulnerabilities from being exploited. However, this approach does not provide complete isolation from network-connected resources, as the device may still be accessible through other active services. Consequently, it does not guarantee total inaccessibility.

A web application firewall (WAF) protects web applications by filtering and monitoring HTTP traffic between a client and a server. While it can defend against specific attacks targeting web applications, it does not isolate a device from network resources. Therefore, it cannot be relied upon to ensure complete inaccessibility of a device.

A network-based Intrusion Detection System (IDS) monitors network traffic for suspicious activities and potential threats. While it can detect intrusion attempts, it does not prevent access to the device itself. As such, it cannot ensure that a device remains inaccessible to network-connected resources.