Modify Program

Adversaries may modify or add a program on a controller to affect how it interacts with the physical process, peripheral devices and other hosts on the network. Modification to controller programs can be accomplished using a Program Download in addition to other types of program modification such as online edit and program append.

Program modification encompasses the addition and modification of instructions and logic contained in Program Organization Units (POU) [1] and similar programming elements found on controllers. This can include, for example, adding new functions to a controller, modifying the logic in existing functions and making new calls from one function to another.

Some programs may allow an adversary to interact directly with the native API of the controller to take advantage of obscure features or vulnerabilities.

ID: T0889
Sub-techniques:  No sub-techniques
Tactic: Persistence
Platforms: Field Controller/RTU/PLC/IED
Version: 1.1
Created: 13 April 2021
Last Modified: 27 September 2022

Procedure Examples

ID Name Description
S1006 PLC-Blaster

PLC-Blaster copies itself to various Program Organization Units (POU) on the target device. The POUs include the Data Block, Function, and Function Block. [2]

S0603 Stuxnet

Stuxnet infects PLCs with different code depending on the characteristics of the target system. An infection sequence consists of code blocks and data blocks that will be downloaded to the PLC to alter its behavior. [3]


ID Mitigation Description
M0947 Audit

Provide the ability to verify the integrity of control logic or programs loaded on a controller. While techniques like CRCs and checksums are commonly used, they are not cryptographically strong and can be vulnerable to collisions. Preferably cryptographic hash functions (e.g., SHA-2, SHA-3) should be used. [4]

M0945 Code Signing

Utilize code signatures to verify the integrity of the installed program on safety or control assets has not been changed.


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

Monitor device application logs that indicate the program has changed, although not all devices produce such logs.

DS0039 Asset Software

Engineering and asset management software will often maintain a copy of the expected program loaded on a controller and may also record any changes made to controller programs. Data from these platforms can be used to identify modified controller programs.

DS0029 Network Traffic Network Traffic Content

Monitor device management protocols for functions that modify programs such as online edit and program append events.

DS0040 Operational Databases Device Alarm

Monitor device alarms that indicate the program has changed, although not all devices produce such alarms.