A modem security communication system for providing access to a computer system having a host computer and a central access controller located at a host location, and user terminals with transponders at a plurality of remote locations. The modem security communication system also includes at least one modem at each of the host and remote locations for interaction with the host computer and transponder, respectively. The transponder is arranged to receive a spoken word from a computer user whereby an analog signal is converted to a digital signal, compressed, encrypted, and transmitted to the host location where it is decrypted and compared with a stored signal on a voiced template corresponding to an identified user's voice. The system further provides for initial communication between the transponder and the host controller to sustain the communication link. This communication may also be encrypted for security. The system also provides for the voice templates to be updated with each authorized access to the computer system.