A processor-based gaming machine running wager-based games can include an exterior housing, a master gaming controller, a display device, and an anonymous player tracking device adapted to detect passively biometric information from players to facilitate the anonymous tracking of gaming activities without the use of traditional player tracking instruments. A player tracking system can include multiple such gaming machines, a database storing a plurality of player profiles that include biometric data, and a remote player tracking server configured to receive passively detected biometric data regarding anonymous players, determine whether the received biometric data is associated with existing player profiles, attribute credit for the anonymous gaming activity if it is, and create a new player profile if it is not. Player profiles can include multiple biometrics for each player, and confidence levels can be associated with a given biometric to a profile and a given gaming session to a profile.