Abstract: This invention discloses a system for determining whether a purported or alleged authorized user is in fact the authorized user, by comparing new data on a real-time basis against probability distribution representations including an authorized user probability distribution representation and a global or wide population probability distribution representation, to provide a probability as to whether the purported authorized user is the authorized user. This invention may utilize keyboard dynamics or data, or X-Y device data, or other data from similar measurable characteristics, to determine the probability that the new data from the purported authorized user indicates or identifies that user as the authorized user. This invention identifies the user continuously as the user interacts with the system and to identify a change in situation in the environment of the user.