False Positive.

What is a false positive?

A false positive is a wrong alarm. NIST SP 800-83 Rev. 1 describes it as an instance in which a security tool incorrectly classifies benign content as malicious. Benign means harmless. NIST SP 800-86 puts it as incorrectly classifying benign activity as malicious. In vulnerability work, NIST SP 800-115 defines it as an alert that incorrectly indicates that a vulnerability is present.

How does a false positive happen?

A security tool decides by rules or by patterns it has learned. When harmless content or activity matches one of them, the tool raises an alert even though nothing is wrong. NIST also gives a statistical meaning. SP 800-90B describes it as an erroneous acceptance of the hypothesis that a statistically significant event has been observed, and says it is also referred to as a type 1 error. A simple illustration: a scanner reports a weakness on a system that does not have it. The wording in these sources is about wrong classification, so the cause can vary by tool.

Why does it matter?

Every alert needs someone to look at it. If many alerts turn out to be wrong, that review time is spent on harmless things. This is reasoning, not a figure from the sources, but it suggests that a tool with many false positives can make real alerts harder to notice. Teams can also lose trust in a tool that is often wrong.

How can you reduce false positives?

The NIST definitions describe what a false positive is, not how to remove it. General approaches are cautious ideas that teams often use.

• Check each alert against what the tool saw before acting on it.
• Record why an alert was judged harmless, so the next reviewer does not repeat the work.
• Tune the rules or settings of the tool where the same harmless activity keeps triggering it.

Tuning should be done with care. Loosening a rule too far can hide real problems.

Is a false positive the same as a false negative?

No. They are opposites. A false positive is a harmless thing wrongly flagged. A false negative is a real threat that the tool misses. The NIST definitions quoted here cover the false positive only, but the reverse case is the natural counterpart.

Is a false positive the same as a low-severity alert?

No. A low-severity alert is a real finding that is judged to matter less. A false positive is not a real finding at all, because the thing flagged is benign or the weakness is not present.