This indicates that an unauthorized DNP3 client issued a request other than a read or write request to a PLC or other field device.
The Distributed Network Protocol (DNP3) is an industry standard for inter-operations between devices and is commonly found in SCADA systems. DNP3 enables data and command exchange between a sever and a client device. The server sends commands and controls the operation of a client device.
DNP3 servers and clients
Limit network access to vulnerable devices. Investigate the source of the traffic to prevent further attacks.