Validating identification clusters formed of unique transmitter intercepts and validating clusters based on information within the cluster data with or without the aid of specific intercepts. Transmitter validation signals are allocated for validating specific ones of the transmitters. Analyzers identify specific received intercepts from specific ones of the transmitters to form an identification signal. Storage is provide for storing the specific received intercepts with corresponding identification clusters for marking the specific identification cluster as validated or invalidated. The valid and invalid states of the stored clusters are used to authorize or prevent access by the transmitters to the communication system.