Active scanning is the process of sending probes or packets to a target system or network and analyzing the responses to gather information or identify vulnerabilities. Active scanning can be intrusive and disruptive, especially in an ICS environment, where availability and reliability are critical. Active scanning can cause unintended consequences, such as triggering alarms, shutting down devices, or affecting physical processes.
Therefore, active scanning is the most likely to cause harm to an ICS environment among the given options.
References:
*The Official CompTIA PenTest+ Study Guide (Exam PT0-002), Chapter 2: Conducting Passive Reconnaissance, page 72-73.
*The Official CompTIA PenTest+ Student Guide (Exam PT0-002) eBook1, Chapter 2: Conducting Passive Reconnaissance, page 2-20.
*Risk Assessment Standards for ICS Environments2, page 8.