A system for identifying the calling device used to place a call in to an enterprise call center. The system also provides information about the network path through which the call was delivered. The system uses active “pinging” in the audio channel during the first few seconds of the call. The device of the invention sends a special sequence of audio tones from the callee to the caller over the audio channel. The system then records and analyses the resulting incoming audio and compares them with the original tones. The system uses that information to characterize the calling device, and possibly the network path as well. The system checks this information against previously stored information from a known valid caller to aid in verifying the identity of the caller, or to flag the call for further assessment via other methods.