1. A method of authenticating a user for a transaction, the method comprising: receiving, at a server computer, a communication indicative of a location of a communication device associated with the user; in response to receiving the communication, retrieving, via the server computer, a reference for accessing a voice model associated with the user, wherein the voice model is stored in a database; receiving, at the server computer, a voice segment from the user; using the reference to access the voice model stored in the database; comparing the received voice segment to the voice model; and determining whether the user is authenticated for the transaction based at least in part on comparing the received voice segment to the voice model.