An Identity Signal is a form of data that can be used to uniquely identify an individual. Common identity signals include entered knowledge (passwords, biographical data), biometric measurements, captured behavioral-biometric data, ambient information sources such as location, network context, or browser fingerprint, and the presence of uniquely identifying objects such as a mobile phone. In multi-factor authentication (MFA), identity signals comprising two or more identity factors (things known, things possessed, or things embodied) are combined to establish a user's identity.