17. A method comprising: receiving, at a computer system, a user identifier and a first password, wherein the user identifier specifies a user, and wherein the first password is to replace a current password used to authenticate the user and, in the event that the first password is successfully established, will replace the current password such that the first password will authenticate the user and the current password will no longer authenticate the user; retrieving, by the computer system, a password preference model for the user identifier from a database, wherein the password preference model is provided from an entry in the database that corresponds to the user identifier, and wherein the password preference model was previously developed by the computer system based on one or more previous passwords successfully established as passwords to authenticate the user, wherein the password preference model describes one or more user tendencies indicated in a content of the previous passwords, wherein the user tendencies comprise one or more of: one or more characteristics, formulas, rules, or other indicia that have been employed by the user identified by the user identifier in creating the content of the previous passwords; determining, by the computer system, a similarity between a content of the first password and the password preference model; and returning, by the computer system, a value indicating a likelihood that the first password was created by the user rather than a third party impersonating the user, wherein the value is based on the similarity.
18. The method of claim 17 , further comprising updating the password preference model in response to an indication that the first password has been established as the current password for the user identifier.