Definition
A false negative occurs when a security system or process fails to detect an actual threat or anomaly, incorrectly classifying it as benign. This means a malicious activity or harmful condition goes unnoticed and unaddressed by the monitoring or detection mechanism. In practice, false negatives represent a critical failure in defensive capabilities, allowing threats to persist undetected within an environment. The impact of a false negative can be severe, potentially leading to data breaches, system compromise, or significant operational disruption. For instance, an intrusion detection system that misses a malware infection is a false negative. This differs from a false positive, which incorrectly flags legitimate activity as malicious. Understanding false negatives is essential for cybersecurity professionals and is a key concept tested on certifications like CompTIA Security+ and CySA+.