FortiGate for application control and intrusion prevention system (IPS): In the control area zones, FortiGate can provide critical security measures such as application control and intrusion prevention. This helps detect and prevent unauthorized activities and threats targeting the OT network.
FortiNAC for network access control: FortiNAC can be used to enforce network access policies, ensuring that only authorized devices and users can access specific zones within the control area, thereby reducing the risk of unauthorized access or breaches.
FortiSIEM for security incident and event management: FortiSIEM provides centralized monitoring and analysis of security incidents and events across the OT environment. It helps to identify potential threats, improve visibility, and ensure quick responses to security incidents.

FortiGate's application control identifies OT traffic by deep-inspecting the industrial protocols carried in the flows (Modbus, DNP3, IEC-104, etc.). It matches protocol signatures to classify the application and enforce policy.

IEC 104 is a widely used protocol in the field of Supervisory Control and Data Acquisition (SCADA) for electrical engineering applications, specifically telecontrol. It's designed to facilitate communication between control stations and substations in power grids.

Planning a threat hunting strategy is essential for proactively searching for threats and vulnerabilities in the OT environment before they manifest into attacks.
Evaluating what can go wrong before it happens is a core part of risk assessment, involving the identification and analysis of potential risks and their impacts on OT systems.
Implementing strategies to automatically bring PLCs offline is generally not a responsible or safe approach in OT environments because it could disrupt critical industrial processes.
Creating disaster recovery plans is important for overall business continuity but is not primarily a task of auditors during risk assessment-it is more of a broader business continuity or incident response responsibility.