14. The computer-readable storage medium of claim 13 , wherein the updating comprises applying a machine learning algorithm to the current password and the one or more previous passwords associated with the user identifier.
14. The computer-readable storage medium of claim 13 , wherein the updating comprises applying a machine learning algorithm to the current password and the one or more previous passwords associated with the user identifier. 15. The computer-readable storage medium of claim 14 , wherein, in the event that a number of the one or more previous passwords is less than a threshold, the password preference model associated with the user identifier is a default password preference model.