1. A method, performed by at least one computer, the method comprising: receiving a communication from an application program executing on a client device different from the at least one computer; identifying from the communication an asserted identity of the application program; and verifying the asserted identity of the application program at least in part by: interacting with the client device to obtain additional information about the application program; and determining whether the additional information about the application program is consistent with the asserted identity of the application program.