What do host-based IDSs monitor?

Host-based Intrusion Detection Systems (IDSs) are specifically designed to monitor and analyze the activities on a single host or device, looking for signs of unauthorized access or unusual behavior that may indicate a security threat. Their primary function is to provide a defense mechanism against threats that may originate from within the host itself or from other malicious sources attempting to exploit vulnerabilities.

The correct choice emphasizes that host-based IDSs focus on detecting unusual activity, but importantly, they do so by analyzing system logs, process behavior, and other indicators within the host system rather than monitoring the network as a whole. This differentiation is crucial because it reflects the targeted nature of host-based systems, which dive deep into the behaviors and operations of individual devices rather than merely observing network traffic.

While the other choices mention aspects like CPU utilization and processes at a particular time, they do not encapsulate the broader function of host-based IDSs, which is focused on identifying unusual patterns and possible attacks that originate from within a host's environment rather than external network activity. This targeted approach allows for better detection of threats specific to the system being monitored, making the emphasis on unusual activity significant in the context of host-based IDS operations.