A method for an authentication server to authenticate Voice over Internet Protocol (VoIP) devices includes receiving a request from a unverified VoIP device to verify its global telephone number over a computer network, searching for verified VoIP devices that have authenticated identities and caller ID service, and providing the telephone numbers of the verified VoIP devices to the unverified VoIP device, wherein the unverified VoIP device calls the verified VoIP devices and the verified VoIP devices detect telephone numbers of the unverified VoIP device. The method further comprises receiving the detected telephone numbers from the verified VoIP devices and determining if the detected telephone numbers match a telephone number provided by the unverified VoIP device, wherein the unverified VoIP device becomes verified if the telephone numbers match the telephone number provided by the VoIP device.