Unauthorized Command Message

Unauthorized Command Message
Technique
ID	T0855
Tactic	Impair Process Control
Data Sources	Alarm history, Sequential event recorder, Netflow/Enclave netflow, Network protocol analysis, Packet capture
Asset	Field Controller/RTU/PLC/IED

Description

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 Maroochy Attack, the adversary used a dedicated analog two-way radio system to send false data and instructions to pumping stations and the central computer.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. Alarms were activated more than a dozen times.34 These disruptions occurred once in 2017, and later in a nearby county in 2019.4

Procedure Examples

• 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.5
• The Industroyer IEC 101 module has the capability to communicate with devices (likely RTUs) via the IEC 101 protocol. The module will attempt to find all Information Object Addresses (IOAs) for the device and attempt to change their state in the following sequence: OFF, ON, OFF.6
• In states 3 and 4 Stuxnet sends two network bursts (done through the DP_SEND primitive). The data in the frames are instructions for the frequency converter drives.7
• Using Triton, an adversary can manipulate the process into an unsafe state from the DCS while preventing the SIS from functioning appropriately.8

Mitigations

• 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).

• 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.9

• Software Process and Device Authentication - Devices should authenticate all messages between master and outstation assets.

• 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.1011912

• 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.

References

1. ^  Bonnie Zhu, Anthony Joseph, Shankar Sastry. (2011). A Taxonomy of Cyber Attacks on SCADA Systems. Retrieved January 12, 2018.
2. ^  Marshall Abrams. (2008, July 23). Malicious Control System Cyber Security Attack Case Study– Maroochy Water Services, Australia. Retrieved March 27, 2018.
3. ^  Zack Whittaker. (2017, April 12). Dallas' emergency sirens were hacked with a rogue radio signal. Retrieved November 6, 2020.
4. a b  Benjamin Freed. (2019, March 13). Tornado sirens in Dallas suburbs deactivated after being hacked and set off. Retrieved November 6, 2020.
5. ^  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 March 27, 2018.
6. ^  Anton Cherepanov, ESET. (2017, June 12). Win32/Industroyer: A new threat for industrial control systems. Retrieved September 15, 2017.

7. ^  Nicolas Falliere, Liam O Murchu, Eric Chien. (2011, February). W32.Stuxnet Dossier (Version 1.4). Retrieved September 22, 2017.
8. ^  Blake Johnson, Dan Caban, Marina Krotofil, Dan Scali, Nathan Brubaker, Christopher Glyer. (2017, December 14). Attackers Deploy New ICS Attack Framework “TRITON” and Cause Operational Disruption to Critical Infrastructure. Retrieved January 12, 2018.
9. a b  Department of Homeland Security. (2016, September). Retrieved September 25, 2020.
10. ^  Karen Scarfone; Paul Hoffman. (2009, September). Guidelines on Firewalls and Firewall Policy. Retrieved September 25, 2020.
11. ^  Keith Stouffer. (2015, May). Guide to Industrial Control Systems (ICS) Security. Retrieved March 28, 2018.
12. ^  Dwight Anderson. (2014). Protect Critical Infrastructure Systems With Whitelisting. Retrieved September 25, 2020.