Apparatus for a cable television subscriber to log onto a computer network with a modem over an upstream path using a USERID and password. The network validates the subscriber USERID and subscriber password with a stored database of valid USERIDs and associated passwords. After the USERID and password are validated, the modem then provides it electronic serial number to the network for validation against a stored database of authorized serial numbers. Upon additional validation of the modem's serial number, the subscriber is authorized to use the network.