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EMB-27: Safety Integrity Level (SIL)

EMB 6 — Medium Identify

Mechanisms exist to assign a Safety Integrity Level (SIL) that measures the performance and reliability with which a Safety Instrumented Function (SIF) reduces risk

Control Question: Does the organization assign a Safety Integrity Level (SIL) that measures the performance and reliability with which a Safety Instrumented Function (SIF) reduces risk?

Capability Maturity Model

Level 0 — Not Performed

Practices are non-existent, based on the inability to demonstrate an implemented and operational capability. A reasonable person would conclude the control is not being performed.

Level 1 — Performed Informally

Embedded Technology (EMB) domain capabilities are ad hoc and inconsistent. Capability criteria associated with this control may include: ▪ Policies, standards & procedures associated with EMB domain capabilities provide limited coverage due to the depth and breadth of the existing documentation. ▪ Embedded technology management-related activities are decentralized (e.g., a localized/regionalized function) and uses non-standardized methods to implement secure, resilient and compliant practices. ▪ Embedded technologies (e.g., Operational Technology (OT) and Internet of Things (IoT) are managed in the same manner as any other technology asset.

Level 2 — Planned & Tracked

Embedded Technology (EMB) capabilities are requirements-driven, but are not standardized across the entity (e.g., local/regional level consistency). Capability criteria associated with this control reasonably expect the following criteria to exist: ▪ Policies and standards associated with EMB domain capabilities are formally documented and centrally-managed by the entity. ▪ Standardized Operating Procedures (SOP) associated with EMB domain capabilities are documented and maintained by process owners. ▪ IT and/or cybersecurity personnel work with business stakeholders and process owners to appropriately scope and reasonably implement cybersecurity and data protection controls associated with EMB domain capabilities to address applicable statutory, regulatory and/or contractual requirements for Technology Assets, Applications, Services and/or Data (TAASD). ▪ Embedded technology-related controls are primarily administrative and preventative in nature (e.g., policies, standards and procedures & guidelines). ▪ Embedded technology management may be a defined function (e.g., team or department) or assigned as an additional duty to existing IT and/or cybersecurity personnel.

Level 3 — Well Defined

Embedded Technology (EMB) capabilities are standardized across the entity for applicability to People, Processes, Technologies, Data and/or Facilities (PPTDF) to ensure consistency for Technology Assets, Applications, Services and/or Data (TAASD). Capability criteria associated with this control reasonably expect the following criteria to exist: ▪ Policies and standards associated with EMB domain capabilities are formally documented and centrally-managed by the entity's Governance, Risk & Compliance (GRC) team, or similar function. ▪ Standardized Operating Procedures (SOP) associated with EMB domain capabilities are well-documented and kept current by process owners. ▪ An embedded systems team, or similar function, is appropriately staffed and supported to implement and maintain EMB domain capabilities. ▪ Technology is leveraged to enhance the efficiency and accuracy of embedded technology operations (e.g., Configuration Management Database (CMBD) Asset Management solution). ▪ The entity's Governance, Risk & Compliance (GRC) team, or similar function, works with business stakeholders and process owners to appropriately scope and reasonably implement cybersecurity and data protection controls associated with EMB domain capabilities to address Minimum Compliance Requirements (MCR) (e.g., applicable statutory, regulatory and/or contractual requirements) and Discretionary Security Requirements (DSR) (e.g., entity-required controls).

Level 4 — Quantitatively Controlled

Embedded Technology (EMB) capabilities, in addition to being standardized across the entity and centrally managed to ensure consistency across Technology Assets, Applications, Services and/or Data (TAASD), efforts are metrics driven to provide sufficient insight for decision makers to predict optimal performance, ensure continued operations and/or identify areas for improvement. Capability criteria associated with this control reasonably expect the following criteria to exist: ▪ Applicable SCR-CMM Level 3 (Well Defined) capabilities are implemented and operational. ▪ Metrics reporting includes quantitative analysis of Key Performance Indicators (KPIs). ▪ Metrics reporting includes quantitative analysis of Key Risk Indicators (KRIs). ▪ Scope of metrics, KPIs and KRIs covers organization-wide cybersecurity and data protection controls, including functions performed by third-parties. ▪ Organizational leadership maintains a formal process to objectively review and respond to metrics, KPIs and KRIs (e.g., monthly or quarterly review). ▪ Based on metrics analysis, process improvement recommendations are submitted for review and are handled in accordance with change control processes. ▪ Business and technical stakeholders are involved in reviewing and approving proposed changes to evolve capabilities.

Level 5 — Continuously Improving

Utilize SCR-CMM Level 3 or Level 4 (if available) criteria definitions: ▪ There are no defined Level 5 criteria, since it is reasonable to assume a continuously-improving process is not necessary to operationalize this control. ▪ Level 5 capabilities should be considered “world-class” where the control builds on Level 4 capabilities, but are continuously improving through Artificial Intelligence (AI) and/or Machine Learning (ML) technologies. ▪ While it may be possible to develop responsive capabilities for this control through the use of AI and/or ML technologies, the criteria would be organization-specific to define.

Assessment Objectives

  1. EMB-27_A01 the methodology used to determine the Safety Integrity Level (SIL) for each Safety Instrumented Function (SIF) (e.g., risk graph or Layer of Protection Analysis (LOPA)) is documented.
  2. EMB-27_A02 a target Safety Integrity Level (SIL) is assigned to each Safety Instrumented Function (SIF) based on the risk reduction required, as determined by a documented hazard and risk assessment.
  3. EMB-27_A03 the achieved Safety Integrity Level (SIL) of each Safety Instrumented Function (SIF) is verified (e.g., through Probability of Failure on Demand (PFD) calculation and architectural constraints) to meet or exceed the assigned target SIL.
  4. EMB-27_A04 Safety Integrity Level (SIL) assignments are re-validated at a defined frequency and when the process, Safety Instrumented System (SIS) design or operating conditions change.

Evidence Requirements

E-EMB-04 Safety Instrumented System (SIS) Documentation

Documented evidence of Safety Instrumented Systems (SIS), Safety Instrumented Functions (SIF), assigned Safety Integrity Levels (SIL) and safety assessments for embedded technologies.

Asset Management

Technology Recommendations

Micro/Small

  • Not applicable unless hazardous processes are operated

Small

  • Vendor-provided safety documentation reviewed
  • Safety requirements documented

Medium

  • Hazard and risk analysis (e.g., HAZOP, LOPA) with SIL assignment
  • SIL verification calculations

Large

  • Functional safety program with documented SIL determination and verification (IEC 61511)
  • Cybersecurity risk assessment of SIS (ISA/IEC 62443-3-2)

Enterprise

  • Enterprise functional safety management with SIL lifecycle tooling
  • Integrated process safety and OT cybersecurity risk assessment
  • Independent functional safety assessment

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