24. The system of claim 18 , wherein the instructions further cause the processor to: in response to receiving multiple text messages that do not satisfy a predetermined criterion, send, to the device at the phone number for the user, a notification that a third party may be attempting to spoof an account of the device at the phone number for the user.
24. The system of claim 18 , wherein the instructions further cause the processor to: in response to receiving multiple text messages that do not satisfy a predetermined criterion, send, to the device at the phone number for the user, a notification that a third party may be attempting to spoof an account of the device at the phone number for the user. 26. The system of claim 24 , wherein the criterion is a rate-limiting criterion and the instructions further cause the processor to: send, to the device, the notification when a quantity of received, non-authenticated text messages directed to the phone number for the user exceeds a predetermined threshold.