The Motorola MOSCAD and ACE line of RTUs through 2022-05-02 omit an authentication requirement. They feature IP Gateway modules which allow for interfacing between Motorola Data Link Communication (MDLC) networks (potentially over a variety of serial, RF and/or Ethernet links) and TCP/IP networks. Communication with RTUs behind the gateway is done by means of the proprietary IPGW protocol (5001/TCP). This protocol does not have any authentication features, allowing any attacker capable of communicating with the port in question to invoke (a subset of) desired functionality.