13. A computer-readable storage device having instructions stored which, when executed by a computing device, cause the computing device to perform operations comprising: receiving a request to confirm a user identity; retrieving a user profile associated with the user identity; generating, based on the user profile and a level of security desired, a text challenge, wherein generating the text challenge is based on eliciting distinctive behavior of the speaker when compared to behavior of other users, the behavior of other users and the highly distinctive behavior of the speaker being stored in a database of dynamic image features; prompting the speaker to utter the text challenge; recording an audio recording and a video recording of the speaker as the speaker utters the text challenge; and performing an analysis of the audio recording and the video recording based on the user profile.
13. A computer-readable storage device having instructions stored which, when executed by a computing device, cause the computing device to perform operations comprising: receiving a request to confirm a user identity; retrieving a user profile associated with the user identity; generating, based on the user profile and a level of security desired, a text challenge, wherein generating the text challenge is based on eliciting distinctive behavior of the speaker when compared to behavior of other users, the behavior of other users and the highly distinctive behavior of the speaker being stored in a database of dynamic image features; prompting the speaker to utter the text challenge; recording an audio recording and a video recording of the speaker as the speaker utters the text challenge; and performing an analysis of the audio recording and the video recording based on the user profile. 14. The computer-readable storage device of claim 13 , wherein the user profile is generated as part of a user enrollment process.