Isa-tr84.00.09 <CERTIFIED>

While the series provides comprehensive security requirements for Industrial Automation and Control Systems (IACS), it is often industry-agnostic. ISA-TR84.00.09 acts as a contextual overlay, applying these security principles specifically to the functional safety domain.

This is where enters the frame. Published by the International Society of Automation (ISA), this technical report provides a formal methodology to bridge the gap between functional safety (IEC 61511) and cybersecurity (IEC 62443).

Cybersecurity wasn’t part of the equation. Why? Because the assumption was that safety networks were air-gapped, proprietary, and obscure. No hacker would bother with a Beckhoff controller or a Triconex when they could go after corporate payroll. isa-tr84.00.09

This wasn’t just a checklist—it was an . It said that safety and security are not separate columns to be reconciled later, but two faces of the same reliability coin.

The 2023/2024 version is a significant update over the 2017 version, growing from 54 pages to over 120 pages, reflecting a much higher level of detail: Network Topology: Includes guidance on Purdue Model reference models. Risk Assessment: Published by the International Society of Automation (ISA),

This was revolutionary. It forced engineers to confront that a “safe” system is actually if an attacker can modify its logic, suppress its alarms, or reset its timers. The report essentially said: Your safety analysis is incomplete without a threat model.

A chemical reactor with a SIF designed to close a feed valve if temperature exceeds 300°C. Required SIL: 2. Because the assumption was that safety networks were

ISA-TR84.00.09 ends, as all great technical reports do, by posing a question that remains unanswered in most plants today:

First, you perform a standard Process Hazard Analysis (PHA) and Layer of Protection Analysis (LOPA) to determine the required SIL for each Safety Instrumented Function (SIF). A SIF requiring SIL 3 is critical; a SIF requiring SIL 1 is less critical.

Ensuring patches and system changes do not degrade safety performance. 3.3. Bow-Tie Analysis