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The adversary is trying to run malicious code.

Execution consists of techniques that result in adversary-controlled code running on a local or remote system, device, or other asset. This execution may also rely on unknowing end users or the manipulation of device operating modes to run. Adversaries may infect remote targets with programmed executables or malicious project files that operate according to specified behavior and may alter expected device behavior in subtle ways. Commands for execution may also be issued from command-line interfaces, APIs, GUIs, or other available interfaces. Techniques that run malicious code may also be paired with techniques from other tactics, particularly to aid network Discovery and Collection, impact operations, and inhibit response functions.

Techniques in this Tactics Category

Below is a list of all the Execution techniques in ATT&CK for ICS:

NameTacticsTechnical Description
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.
Command-Line InterfaceExecutionAdversaries may utilize command-line interfaces (CLIs) to interact with systems and execute commands. CLIs provide a means of interacting with computer systems and are a common feature across many types of platforms and devices within control systems environments.1 Adversaries may also use CLIs to install and run new software, including malicious tools that may be installed over the course of an operation.

CLIs are typically accessed locally, but can also be exposed via services, such as SSH, Telnet, and RDP. Commands that are executed in the CLI execute with the current permissions level of the process running the terminal emulator, unless the command specifies a change in permissions context.

Many controllers have CLI interfaces for management purposes.
Execution through APIExecutionAdversaries may attempt to leverage Application Program Interfaces (APIs) used for communication between control software and the hardware. Specific functionality is often coded into APIs which can be called by software to engage specific functions on a device or other software, such as Change Program State of a program on a PLC.
Graphical User InterfaceExecutionAdversaries may attempt to gain access to a machine via a Graphical User Interface (GUI) to enhance execution capabilities. Access to a GUI allows a user to interact with a computer in a more visual manner than a CLI. A GUI allows users to move a cursor and click on interface objects, with a mouse and keyboard as the main input devices, as opposed to just using the keyboard.

If physical access is not an option, then access might be possible via protocols such as VNC on Linux-based and Unix-based operating systems, and RDP on Windows operating systems. An adversary can use this access to execute programs and applications on the target machine.

In the 2015 attack on the Ukrainian power grid, the adversary utilized the GUI of HMIs in the SCADA environment to open breakers.2
Man in the MiddleExecutionAdversaries with privileged network access may seek to modify network traffic in real time using man-in-the-middle (MITM) attacks.3 This type of attack allows the adversary to intercept traffic to and/or from a particular device on the network. If a MITM attack is established, then the adversary has the ability to block, log, modify, or inject traffic into the communication stream. There are several ways to accomplish this attack, but some of the most-common are Address Resolution Protocol (ARP) poisoning and the use of a proxy.4

A MITM attack may allow an adversary to perform the following attacks:

Block Reporting Message, Spoof Reporting Message, Modify Parameter,

Unauthorized Command Message
Program Organization UnitsLateral Movement
Program Organizational Units (POUs) are block structures used within PLC programming to create programs and projects.5 POUs can be used to hold user programs written in IEC 61131-3 languages: Structured text, Instruction list, Function block, and Ladder logic.6 They can also provide additional functionality, such as establishing connections between the PLC and other devices using TCON.7

Stuxnet uses a simple code-prepending infection technique to infect Organization Blocks (OB). For example, the following sequence of actions is performed when OB1 is infected 8:

  • Increase the size of the original block.
  • Write malicious code to the beginning of the block.
  • Insert the original OB1 code after the malicious code.
Project File InfectionPersistence
Adversaries may attempt to infect project files with malicious code. These project files may consist of objects, program organization units, variables such as tags, documentation, and other configurations needed for PLC programs to function.9 Using built in functions of the engineering software, adversaries may be able to download an infected program to a PLC in the operating environment enabling further execution and persistence techniques.10 Adversaries may export their own code into project files with conditions to execute at specific intervals.8 Malicious programs allow adversaries control of all aspects of the process enabled by the PLC. Once the project file is downloaded to a PLC the workstation device may be disconnected with the infected project file still executing.10
ScriptingExecutionAdversaries may use scripting languages to execute arbitrary code in the form of a pre-written script or in the form of user-supplied code to an interpreter. Scripting languages are programming languages that differ from compiled languages, in that scripting languages use an interpreter, instead of a compiler. These interpreters read and compile part of the source code just before it is executed, as opposed to compilers, which compile each and every line of code to an executable file. Scripting allows software developers to run their code on any system where the interpreter exists. This way, they can distribute one package, instead of precompiling executables for many different systems. Scripting languages, such as Python, have their interpreters shipped as a default with many Linux distributions. In addition to being a useful tool for developers and administrators, scripting language interpreters may be abused by the adversary to execute code in the target environment. Due to the nature of scripting languages, this allows for weaponized code to be deployed to a target easily, and leaves open the possibility of on-the-fly scripting to perform a task.
User ExecutionExecutionAdversaries may rely on a targeted organizations’ user interaction for the execution of malicious code. User interaction may consist of installing applications, opening email attachments, or granting higher permissions to documents. Adversaries may embed malicious code or visual basic code into files such as Microsoft Word and Excel documents or software installers.11 Execution of this code requires that the user enable scripting or write access within the document. Embedded code may not always be noticeable to the user especially in cases of trojanized software.12