Unauthorized Command Message

Adversaries may send unauthorized command messages to instruct control system assets to perform actions outside of their intended functionality, or without the logical preconditions to trigger their expected function. Command messages are used in ICS networks to give direct instructions to control systems devices. If an adversary can send an unauthorized command message to a control system, then it can instruct the control systems device to perform an action outside the normal bounds of the device's actions. An adversary could potentially instruct a control systems device to perform an action that will cause an Impact. [1]

In the Dallas Siren incident, adversaries were able to send command messages to activate tornado alarm systems across the city without an impending tornado or other disaster. [2] [3]

ID: T0855
Sub-techniques:  No sub-techniques
Platforms: None
Version: 1.2
Created: 21 May 2020
Last Modified: 13 October 2023

Procedure Examples

ID Name Description
C0028 2015 Ukraine Electric Power Attack

During the 2015 Ukraine Electric Power Attack, Sandworm Team issued unauthorized commands to substation breaks after gaining control of operator workstations and accessing a distribution management system (DMS) application. [4]

C0034 2022 Ukraine Electric Power Attack

During the 2022 Ukraine Electric Power Attack, Sandworm Team used the MicroSCADA SCIL-API to specify a set of SCADA instructions, including the sending of unauthorized commands to substation devices.[5]


INCONTROLLER can send custom Modbus commands to write register values on Schneider PLCs.[6]

INCONTROLLER can send write tag values on OPC UA servers.[6]

S0604 Industroyer

Using its protocol payloads, Industroyer sends unauthorized commands to RTUs to change the state of equipment. [7]

S1072 Industroyer2

Industroyer2 is capable of sending command messages from the compromised device to target remote stations to open data channels, retrieve the location and values of Information Object Addresses (IOAs), and modify the IO state values through Select Before Operate I/O, Select/Execute, and Invert Default State operations.[8][9]

C0020 Maroochy Water Breach

In the Maroochy Water Breach, the adversary used a dedicated analog two-way radio system to send false data and instructions to pumping stations and the central computer.[10]

C0030 Triton Safety Instrumented System Attack

In the Triton Safety Instrumented System Attack, TEMP.Veles leveraged Triton to send unauthorized command messages to the Triconex safety controllers.[11]

Targeted Assets

ID Asset
A0007 Control Server
A0002 Human-Machine Interface (HMI)
A0005 Intelligent Electronic Device (IED)
A0003 Programmable Logic Controller (PLC)
A0004 Remote Terminal Unit (RTU)
A0010 Safety Controller


ID Mitigation Description
M0802 Communication Authenticity

Protocols used for control functions should provide authenticity through MAC functions or digital signatures. If not, utilize bump-in-the-wire devices or VPNs to enforce communication authenticity between devices that are not capable of supporting this (e.g., legacy controllers, RTUs).

M0937 Filter Network Traffic

Perform inline allowlisting of automation protocol commands to prevent devices from sending unauthorized command or reporting messages. Allow/denylist techniques need to be designed with sufficient accuracy to prevent the unintended blocking of valid messages.

M0807 Network Allowlists

Use host-based allowlists to prevent devices from accepting connections from unauthorized systems. For example, allowlists can be used to ensure devices can only connect with master stations or known management/engineering workstations. [12]

M0930 Network Segmentation

Segment operational assets and their management devices based on their functional role within the process. Enabling more strict isolation to more critical control and operational information within the control environment. [13] [14] [12] [15]

M0813 Software Process and Device Authentication

Devices should authenticate all messages between master and outstation assets.

M0818 Validate Program Inputs

Devices and programs that receive command messages from remote systems (e.g., control servers) should verify those commands before taking any actions on them.


ID Data Source Data Component Detects
DS0015 Application Log Application Log Content

Monitor for anomalous or unexpected commands that may result in changes to the process operation (e.g., discrete write, logic and device configuration, mode changes) observable via asset application logs.

DS0029 Network Traffic Network Traffic Content

Monitor for unexpected ICS protocol command functions to controllers from existing master devices (including from new processes) or from new devices. The latter is like detection for Rogue Master but requires ICS function level insight to determine if an unauthorized device is issuing commands (e.g., a historian).

Monitoring for unexpected or problematic values below the function level will provide better insights into potentially malicious activity but at the cost of additional false positives depending on the underlying operational process.

Network Traffic Flow

Monitor for new or unexpected connections to controllers, which could indicate an Unauthorized Command Message being sent via Rogue Master.

DS0040 Operational Databases Process History/Live Data

Monitor industrial process history data for events that correspond with command message functions, such as setpoint modification or changes to system status for key devices. This will not directly detect the technique’s execution, but instead may provide additional evidence that the technique has been used and may complement other detections.

Process/Event Alarm

Monitor for anomalous or unexpected commands that may result in changes to the process operation (e.g., discrete write, logic and device configuration, mode changes) observable via asset application logs.