Impair Process Control

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The adversary is trying to manipulate, disable, or damage physical control processes.

Impair Process Control consists of techniques that adversaries use to disrupt control logic and cause determinantal effects to processes being controlled in the target environment. Targets of interest may include active procedures or parameters that manipulate the physical environment. These techniques can also include prevention or manipulation of reporting elements and control logic. If an adversary has modified process functionality, then they may also obfuscate the results, which are often self-revealing in their impact on the outcome of a product or the environment. The direct physical control these techniques exert may also threaten the safety of operators and downstream users, which can prompt response mechanisms. Adversaries may follow up with or use Inhibit Response Function techniques in tandem, to assist with the successful abuse of control processes to result in Impact.

Techniques in this Tactics Category

Below is a list of all the Impair Process Control techniques in ATT&CK for ICS:

NameTacticsTechnical Description
Brute Force I/OImpair Process ControlAdversaries may brute force I/O addresses on a device and attempt to exhaustively perform an action. By enumerating the full range of I/O addresses, an adversary may manipulate a process function without having to target specific I/O interfaces. More than one process function manipulation and enumeration pass may occur on the targeted I/O range in a brute force attempt.
Change Program StateExecution
Impair Process Control
Adversaries may attempt to change the state of the current program on a control device. Program state changes may be used to allow for another program to take over control or be loaded onto the device.
Impair Process Control
Adversaries may use masquerading to disguise a malicious application or executable as another file, to avoid operator and engineer suspicion. Possible disguises of these masquerading files can include commonly found programs, expected vendor executables and configuration files, and other commonplace application and naming conventions. By impersonating expected and vendor-relevant files and applications, operators and engineers may not notice the presence of the underlying malicious content and possibly end up running those masquerading as legitimate functions. Applications and other files commonly found on Windows systems or in engineering workstations have been impersonated before. This can be as simple as renaming a file to effectively disguise it in the ICS environment.
Modify Control LogicImpair Process Control
Inhibit Response Function
Adversaries may place malicious code in a system, which can cause the system to malfunction by modifying its control logic. Control system devices use programming languages (e.g. relay ladder logic) to control physical processes by affecting actuators, which cause machines to operate, based on environment sensor readings. These devices often include the ability to perform remote control logic updates.

Program code is normally edited in a vendor-specific Integrated Development Environment (IDE) that relies on proprietary tools and features. These IDEs allow an engineer to perform host target development and may have the ability to run the code on the machine it is programmed for. The IDE will transmit the control logic to the testing device, and will perform the required device-specific functions to apply the changes and make them active.

An adversary may attempt to use this host target IDE to modify device control logic. Even though proprietary tools are often used to edit and update control logic, the process can usually be reverse-engineered and reproduced with open-source tools.

An adversary can de-calibrate a sensor by removing functions in control logic that account for sensor error. This can be used to change a control process without actually spoofing command messages to a controller or device.

It is believed this process happened in the lesser known over-pressurizer attacks build into Stuxnet. Pressure sensors are not perfect at translating pressure into an analog output signal, but their errors can be corrected by calibration. The pressure controller can be told what the “real” pressure is for given analog signals and then automatically linearize the measurement to what would be the “real” pressure. If the linearization is overwritten by malicious code on the S7-417 controller, analog pressure readings will be “corrected” during the attack by the pressure controller, which then interprets all analog pressure readings as perfectly normal pressure no matter how high or low their analog values are. The pressure controller then acts accordingly by never opening the stage exhaust valves. In the meantime, actual pressure keeps rising.1

In the Maroochy Attack, Vitek Boden gained remote computer access to the control system and altered data so that whatever function should have occurred at affected pumping stations did not occur or occurred in a different way. The software program installed in the laptop was one developed by Hunter Watertech for its use in changing configurations in the PDS computers. This ultimately led to 800,000 liters of raw sewage being spilled out into the community.2
Modify ParameterImpair Process ControlAdversaries may modify parameters used to instruct industrial control system devices. These devices operate via programs that dictate how and when to perform actions based on such parameters. Such parameters can determine the extent to which an action is performed and may specify additional options. For example, a program on a control system device dictating motor processes may take a parameter defining the total number of seconds to run that motor.

An adversary can potentially modify these parameters to produce an outcome outside of what was intended by the operators. By modifying system and process critical parameters, the adversary may cause Impact to equipment and/or control processes. Modified parameters may be turned into dangerous, out-of-bounds, or unexpected values from typical operations. For example, specifying that a process run for more or less time than it should, or dictating an unusually high, low, or invalid value as a parameter.

In the Maroochy Attack, Vitek Boden gained remote computer access to the control system and altered data so that whatever function should have occurred at affected pumping stations did not occur or occurred in a different way. The software program installed in the laptop was one developed by Hunter Watertech for its use in changing configurations in the PDS computers. This ultimately led to 800,000 liters of raw sewage being spilled out into the community.2
Module FirmwarePersistence
Impair Process Control
Adversaries may install malicious or vulnerable firmware onto modular hardware devices. Control system devices often contain modular hardware devices. These devices may have their own set of firmware that is separate from the firmware of the main control system equipment.

This technique is similar to System Firmware, but is conducted on other system components that may not have the same capabilities or level of integrity checking. Although it results in a device re-image, malicious device firmware may provide persistent access to remaining devices.3

An easy point of access for an adversary is the Ethernet card, which may have its own CPU, RAM, and operating system. The adversary may attack and likely exploit the computer on an Ethernet card. Exploitation of the Ethernet card computer may enable the adversary to accomplish additional attacks, such as the following:3

  • Delayed Attack - The adversary may stage an attack in advance and choose when to launch it, such as at a particularly damaging time.
  • Brick the Ethernet Card - Malicious firmware may be programmed to result in an Ethernet card failure, requiring a factory return.
  • "Random" Attack or Failure - The adversary may load malicious firmware onto multiple field devices. Execution of an attack and the time it occurs is generated by a pseudo-random number generator.
  • A Field Device Worm - The adversary may choose to identify all field devices of the same model, with the end goal of performing a device-wide compromise.
  • Attack Other Cards on the Field Device - Although it is not the most important module in a field device, the Ethernet card is most accessible to the adversary and malware. Compromise of the Ethernet card may provide a more direct route to compromising other modules, such as the CPU module.
Program DownloadPersistence
Impair Process Control
Inhibit Response Function
Adversaries may perform a program download to load malicious or unintended program logic on a device as a method of persistence or to disrupt response functions or process control. Program download onto devices, such as PLCs, allows adversaries to implement custom logic. Malicious PLC programs may be used to disrupt physical processes or enable adversary persistence. The act of a program download will cause the PLC to enter a STOP operation state, which may prevent response functions from operating correctly.
Rogue Master DeviceEvasion
Impair Process Control
Adversaries may setup a rogue master to leverage control server functions to communicate with slave devices. A rogue master device can be used to send legitimate control messages to other control system devices, affecting processes in unintended ways. It may also be used to disrupt network communications by capturing and receiving the network traffic meant for the actual master device. Impersonating a master device may also allow an adversary to avoid detection. In the Maroochy Attack, Vitek Boden falsified network addresses in order to send false data and instructions to pumping stations.2
Service StopImpair Process ControlAdversaries may stop or disable services on a system to render those services unavailable to legitimate users. Stopping critical services can inhibit or stop response to an incident or aid in the adversary's overall objectives to cause damage to the environment.4 Services may not allow for modification of their data stores while running. Adversaries may stop services in order to conduct Data Destruction.4
Spoof Reporting MessageEvasion
Impair Process Control
Adversaries may spoof reporting messages in control system environments for evasion and to impair process control. In control systems, reporting messages contain telemetry data (e.g., I/O values) pertaining to the current state of equipment and the industrial process. Reporting messages are important for monitoring the normal operation of a system or identifying important events such as deviations from expected values.

If an adversary has the ability to Spoof Reporting Messages, they can impact the control system in many ways. The adversary can Spoof Reporting Messages that state that the process is operating normally, as a form of evasion. The adversary could also Spoof Reporting Messages to make the defenders and operators think that other errors are occurring in order to distract them from the actual source of a problem.5

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
Unauthorized Command MessageImpair Process ControlAdversaries may send unauthorized command messages to instruct control systems devices to perform actions outside their expected functionality for process control. 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.5

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 2015 attack on the Ukranian power grid, the adversaries gained access to the control networks of three different energy companies. The adversaries used valid credentials to seize control of operator workstations and access a distribution management system (DMS) client application via a VPN. The adversaries used these tools to issue unauthorized commands to breakers at substations which caused a loss of power to over 225,000 customers over various areas.6