What is meant by a "True Negative" in intrusion detection systems?

A "True Negative" in intrusion detection systems refers to a situation where normal activities are correctly classified and not flagged as suspicious or malicious. This indicates that the system effectively distinguishes between benign activities and potential threats, demonstrating its accuracy in recognizing what constitutes normal behavior within a network or system.

Recognizing true negatives is crucial for the performance of an intrusion detection system, as it helps avoid alert fatigue among security analysts who could become overwhelmed by false positives—normal activities mistakenly identified as attacks. In contrast, options that describe incorrect behavior, such as misidentifying a normal activity as an attack or flagging all traffic as malicious, highlight situations where the system lacks precision. Thus, identifying a true negative indicates a successful and functioning intrusion detection approach.