What do we refer to when describing the biometric identification characteristic of "What you are"?

The biometric identification characteristic described as "What you are" refers to the physical attributes unique to an individual. This encompasses inherent biological traits such as fingerprints, facial recognition, iris patterns, and DNA, which are distinct and stable features that can be used for identification purposes.

Physical biometrics provides reliable and often more secure means of authentication because these traits are difficult to replicate or forge, making them an effective security measure in identity and access management. This characteristic contrasts with behavioral traits, which are based on how a person acts or behaves (such as typing rhythm or voice recognition), or dynamic traits that may change over time or in response to different conditions. Challenge/Response systems are also distinct from biometrics as they involve a user responding to a security prompt rather than relying on biometric measurement. The specificity of physical characteristics makes this the correct answer in the context of identity verification.