ETHERSIO (Ether-S-I/O) is an Industrial Control System (ICS) or Supervisory Control And Data Acquisition (SCADA) protocol. It is used for data transfer between PLCs (Programmable Logic Controller) and remote input/output devices (RIOs) manufactured by Saia-Burgess Controls Ltd. A "Smart remote input/output station (Smart RIO)" features physical inputs and outputs and contains a CPU on which a small application can be run. The inputs from these RIO stations can be read and written by the master station (a PLC) using the Ether-S-I/O protocol. The application which can be run on the RIO station is uploaded to the RIO station using the EtherSBus protocol.

This SonicWALL signature identifies legitimate EHTERSIO protocol traffic.