Will your safety function survive a security change?

A firewall update, a maintenance login or a controller patch can affect equipment that protects people. IEC TR 63069:2019 provides guidance on applying IEC 61508 functional safety and the IEC 62443 cybersecurity series together in industrial measurement, control and automation. It is a Technical Report that helps coordinate these disciplines. It does not replace either series or create a combined SIL/SL rating.

Start with the physical consequence

The functional safety question is whether a safety function will perform correctly when needed. IEC 61508-1 addresses the general lifecycle, IEC 61508-2 covers system and hardware requirements, and IEC 61508-3 addresses software. A cybersecurity review asks how unauthorized access or changes could undermine that protection. Consider a pressure-control system: an attack might cause an unsafe pressure increase and also interfere with the shutdown function intended to limit its consequences.

IEC 62443-3-2 risk assessment therefore needs to consider harm to people and the environment, alongside production losses. The zones and conduits model makes access paths visible. A shared engineering workstation or maintenance connection may expose both the control system and its protective functions. IEC 62443-3-3 system requirements help define the technical security measures for the resulting architecture.

Two different ratings, two different questions

SIL determination concerns the safety integrity required of a safety function. SIL 2 cannot be converted into SL 2; matching numbers do not imply matching protection. Within cybersecurity, SL-T, SL-C and SL-A distinguish the target, capability and achieved security levels. SL-T comes from the risk assessment. SL-C describes capability within a defined product or system scope, while SL-A concerns what has actually been achieved. A capable device does not, by itself, establish the security level of an entire installation.

Three situations worth reviewing together

These are worked application scenarios to illustrate the coordination problem, rather than a reproduction of the report's clauses.

A login is only the beginning of access control

Identification and authentication establish who is connecting. Use control determines what that identity may do. Viewing diagnostics and rewriting a safety program deserve different permissions. System integrity concerns protection of programs and configuration, while restricted data flow limits communication paths. For a practical maintenance arrangement, define the access window, the parameters that may be changed and the person who authorizes each change.

Keep ownership clear throughout the lifecycle

The responsibilities extend beyond the product supplier. IEC 62443-2-1 addresses the asset owner's operational security program, and IEC 62443-2-4 covers service-provider processes during integration and maintenance. IEC 62443-4-1 focuses on secure product development and maintenance. A product developed through a secure lifecycle still needs an appropriate installation, operating procedures and controlled maintenance access.

IEC TR 62443-2-3 patch management addresses patch information and activities involving suppliers and asset owners. The installation decision must weigh exposure to the vulnerability against the operational effects of the change. An illustrative change record could identify affected versions, test results, a maintenance window, backup and rollback arrangements, safety-function checks and the person approving the return to service.

Contain the incident while preserving protection

Timely response to events and resource availability need coordinated decisions. A safe state does not always mean removing all power. The process hazards determine how control and protection should behave during network isolation. The seven foundational requirements provide a useful way to review security measures together. For machinery projects, IEC TS 63074 deals more directly with cybersecurity threats that could compromise safety-related control systems.