A false positive is an alert or detection result that appears suspicious but does not represent the harmful activity the rule was intended to catch.
A false positive is an alert or detection result that appears suspicious but does not actually represent the harmful activity the rule was meant to catch. In plain language, it is a security warning that turns out not to be the problem it seemed to indicate.
False positives matter because they consume analyst time and contribute directly to Alert Fatigue. Too many low-value alerts make it harder for teams to focus on genuinely important cases.
They also matter because some security controls, such as blocking systems, can disrupt legitimate work if false positives are not tuned down. Detection accuracy is not only about finding bad activity; it is also about avoiding unnecessary noise and disruption.
| Source | Why it happens |
|---|---|
| Broad rules | Too many normal actions match |
| Missing context | Legitimate activity looks suspicious |
| Outdated logic | Environment changed since tuning |
False positives appear in Detection Rule tuning, Incident Triage, SIEM, EDR, Web Application Firewall, and Intrusion Prevention System operations. Teams review them to improve rule logic, thresholds, context, and workflow.
Security teams track false positives because they are a key signal of whether detections are useful in practice.
A detection rule flags a standard administrative workflow as suspicious every time a legitimate maintenance script runs. The rule is technically firing as designed, but the result is a false positive because it is not identifying the harmful behavior the team actually cares about.
A false positive is not the same as a rule that never fires. It is a case where the rule does fire, but the alert does not represent the intended threat.
It is also different from a False Negative, which is the opposite problem: harmful activity that the system fails to catch.