The terms “false positive” and “true positive” are commonly used in security alerting, but their meaning is often oversimplified. In practice, these terms describe how observed activity relates to detection logic, not definitive outcomes.
What a False Positive Is
In the context of security alerts, a false positive occurs when a detection system correctly identifies activity that matches its criteria, but that activity does not represent the condition the detection was intended to identify.
A false positive reflects how detection logic is defined and applied. It does not indicate a failure of the system. The alert is functioning as designed by surfacing activity that meets specific observable characteristics, even when those characteristics are present for benign or expected reasons.
What a True Positive Is
A true positive occurs when an alert corresponds to activity that aligns with the condition the detection was designed to surface.
Whether an alert is considered a true positive depends on context and interpretation. Confirmation is based on understanding the environment, the activity involved, and how the detection criteria relate to real-world behavior. A true positive does not imply certainty beyond the scope of the alert or automatic significance.
Why False Positives Exist
Detection systems operate under uncertainty. They observe signals rather than intent or outcome.
False positives exist because:
- Detection logic prioritizes visibility over omission
- Many technical behaviors overlap between expected and unexpected activity
- Systems must account for incomplete or ambiguous data
- Broad conditions are used to ensure relevant activity is surfaced
These tradeoffs are inherent to monitoring complex environments and are intentionally accepted as part of detection design.
Why the Distinction Is Not Always Clear
Alerts are not always immediately classifiable as false or true positives.
This ambiguity can result from:
- Partial or delayed data
- Limited visibility into surrounding activity
- Environmental variability
- Changes in system behavior over time
As a result, classification may remain provisional or evolve as additional context becomes available.
Common Misunderstandings
- Believing alerts must be immediately classified as false or true
- Treating false positives as wasted or invalid output
- Assuming true positives always indicate severe conditions
- Expecting detection systems to perfectly distinguish outcomes
- Interpreting classification as a judgment rather than a description
- Assuming classifications are permanent or universally agreed upon
How This Site Uses These Terms
This site uses “false positive” and “true positive” as descriptive terms that explain how alerts relate to detection logic and observed activity.
Alerts are documented based on what they represent and how they are generated, not on how they should be handled or prioritized. These terms are used to support understanding, not to assign value or outcome.