A system detects abnormalities in a call signal indicative of call fraud. The system includes a first device situated in an originating call network and configured to send call signals to a second device situated in a terminating call network. The first device is coupled to a first registry to which it sends the call data from the sent signals for storage as originating call records. The second device is coupled to a second registry to which it sends the call data from the received signals for storage as terminating call records. The first and second registries exchange verification requests and responses to detect whether discrepancies exist between the stored originating call records in the first registry and stored terminating call records in the second registry. The registries generate alerts based on detected discrepancies, which may be used by the devices to block the call fraud.