Calls initiated from disconnected phone numbers and calls initiated from phone numbers that initiate calls to disconnected numbers can be indicative of robocalls. Disconnected numbers and phone numbers that have initiated calls to disconnected numbers are identified and assigned a robocall score that indicates a likelihood that a call initiated from that number is a robocall. A communication network that subscribes to a robocall detection service can request a robocall score associated with an originating number associated with a received call, and then handle the call according to the robocall score.