False Negative

A false negative is a security system failure where a genuine threat or malicious activity goes undetected and is incorrectly classified as benign.

This occurs when cybersecurity tools, such as antivirus software, intrusion detection systems, or endpoint protection platforms, fail to identify actual malware, suspicious network traffic, or other security incidents that should have triggered an alert.

False negatives are particularly dangerous because they create a false sense of security, allowing attackers to operate undetected within systems or networks. Unlike false positives, which generate unnecessary alerts but don't compromise security, false negatives represent actual security gaps that can lead to successful breaches, data theft, or system compromise.

Common causes include outdated signature databases, zero-day exploits that haven't been previously identified, sophisticated evasion techniques used by attackers, or misconfigured security tools. Organizations typically measure false negative rates as part of their security effectiveness metrics, striving to minimize them through regular updates, tuning security systems, implementing layered defense strategies, and conducting regular penetration testing to identify detection gaps.