When a user who should not be allowed access is granted access during authentication, what is this outcome called?

• A. False Positive
• B. False Negative
• C. True Positive
• D. True Negative

Answer: (A)

In authentication, we distinguish whether the system’s decision to grant or deny access matches reality. If someone who should not be allowed in is granted access, the system has wrongly accepted an unauthorized user. This is a false positive (also called a false acceptance). It means the authentication process accepted someone who should have been rejected, which is a serious security risk.

To contrast briefly: a true positive is correctly granting access to an authorized user, a true negative is correctly denying access to an unauthorized user, and a false negative is incorrectly denying access to someone who should be allowed. In security systems, minimizing false positives (and their related metric, the false acceptance rate in biometrics) is crucial because letting in unauthorized users undermines protection.