Patch management is the process of applying software updates to fix security vulnerabilities, improve functionality, or enhance performance. Patch management is an essential part of cybersecurity, as unpatched systems can be exploited by malicious actors. However, patch management for industrial automation and control systems (IACS) is more challenging than for business systems, because patching a live automation system can create safety risks. According to the ISA/IEC 62443 standards, patching an IACS may have the following potential impacts1:

Patching may introduce new vulnerabilities or errors that compromise the availability, integrity, or confidentiality of the IACS.

Patching may affect the functionality or performance of the IACS, causing unexpected or undesired behavior, such as process shutdowns, slowdowns, or failures.

Patching may require downtime or reduced operation of the IACS, which may affect production, quality, or profitability.

Patching may require additional resources, such as personnel, equipment, or testing facilities, which may not be readily available or affordable.

Therefore, patch management for IACS requires careful planning, testing, and validation before applying patches to the operational environment. The ISA/IEC 62443 standards provide guidance and best practices for patch management in the IACS environment, such as1:

Establishing a patch management program that defines roles, responsibilities, policies, and procedures for patching IACS components and systems.

Identifying and prioritizing the IACS assets that need patching, based on their criticality, vulnerability, and risk level.

Evaluating and verifying the patches for compatibility, functionality, and security before applying them to the IACS.

Implementing and documenting the patching process, including backup, recovery, and rollback procedures, in case of patch failure or adverse effects.

Monitoring and auditing the patching activities and outcomes, and reporting any issues or incidents.