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T0855 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. 2

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. 3 1

Item Value
ID T0855
Tactics TA0106
Platforms Field Controller/RTU/PLC/IED
Version 1.2
Created 21 May 2020
Last Modified 05 April 2023

Procedure Examples

ID Name Description
S1045 INCONTROLLER INCONTROLLER can send custom Modbus commands to write register values on Schneider PLCs.8
S0604 Industroyer Using its protocol payloads, Industroyer sends unauthorized commands to RTUs to change the state of equipment. 9
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.1011
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.13
G0034 Sandworm Team In the Ukraine 2015 Incident, Sandworm Team issued unauthorized commands to substation breakers after gaining control of operator workstations and accessing a distribution management system (DMS) client application. 12


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. 6
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. 4 5 6 7
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
DS0015 Application Log Application Log Content
DS0029 Network Traffic Network Traffic Content
DS0040 Operational Databases Process History/Live Data


  1. Benjamin Freed 2019, March 13 Tornado sirens in Dallas suburbs deactivated after being hacked and set off Retrieved. 2020/11/06  

  2. Bonnie Zhu, Anthony Joseph, Shankar Sastry 2011 A Taxonomy of Cyber Attacks on SCADA Systems Retrieved. 2018/01/12  

  3. Zack Whittaker 2017, April 12 Dallas’ emergency sirens were hacked with a rogue radio signal Retrieved. 2020/11/06  

  4. Karen Scarfone; Paul Hoffman 2009, September Guidelines on Firewalls and Firewall Policy Retrieved. 2020/09/25  

  5. Keith Stouffer 2015, May Guide to Industrial Control Systems (ICS) Security Retrieved. 2018/03/28  

  6. Department of Homeland Security 2016, September Retrieved. 2020/09/25  

  7. Dwight Anderson 2014 Protect Critical Infrastructure Systems With Whitelisting Retrieved. 2020/09/25  

  8. DHS/CISA. (2022, May 25). Alert (AA22-103A) APT Cyber Tools Targeting ICS/SCADA Devices. Retrieved September 28, 2022. 

  9. Anton Cherepanov, ESET 2017, June 12 Win32/Industroyer: A new threat for industrial control systems Retrieved. 2017/09/15  

  10. Daniel Kapellmann Zafra, Raymond Leong, Chris Sistrunk, Ken Proska, Corey Hildebrandt, Keith Lunden, Nathan Brubaker. (2022, April 25). INDUSTROYER.V2: Old Malware Learns New Tricks. Retrieved March 30, 2023. 

  11. Forescout. (2022, July 14). Industroyer2 and INCONTROLLER In-depth Technical Analysis of the Most Recent ICS-specific Malware. Retrieved March 30, 2023. 

  12. Electricity Information Sharing and Analysis Center; SANS Industrial Control Systems 2016, March 18 Analysis of the Cyber Attack on the Ukranian Power Grid: Defense Use Case Retrieved. 2018/03/27  

  13. Marshall Abrams 2008, July 23 Malicious Control System Cyber Security Attack Case Study Maroochy Water Services, Australia Retrieved. 2018/03/27