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ISA 99.00.01 “Security Zones and Conduits”

ISA 99.00.01 “Security Zones and Conduits”. The challenge to map ISA 99.00.01 to ISA 99.00.04. Presented to ISA 99 WG04 Dennis Holstein holsteindk@ieee.org. ISA 99 WG 04 Meeting Scottsdale, AZ 25-27 June 2007. What is the challenge. ISA 99.00.01 contains Definitions and Models

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ISA 99.00.01 “Security Zones and Conduits”

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  1. ISA 99.00.01“Security Zones and Conduits” The challenge to map ISA 99.00.01 to ISA 99.00.04 Presented to ISA 99 WG04 Dennis Holstein holsteindk@ieee.org ISA 99 WG 04 Meeting Scottsdale, AZ 25-27 June 2007

  2. What is the challenge • ISA 99.00.01 contains Definitions and Models • Definitions are not the problem • Models are abstract – instantiation for Part 4 is the challenge • ISA 99.00.04 is a compliance specification • Compliance requires testability criteria • By measurement • By inspection and analysis • To be testable requirements must be prescriptive • But, Part 4 must not define “how to” implement the requirements – it must state “what is” required

  3. Apply lessons learned from IEC 62443-3 • IEC TC65WG10 approach • Establish a common reference model defining zones and conduits • Served well for analysis and contributions by independent work packages • Overlaps in the reference model resulted in duplication of requirements and divergent specifications • The challenge was to harmonize the contributions • The approach was to cast the requirements in the context of a security policy statement • This resulted in the generation of a Public Available Specification (PAS) – which is a non-binding document in Europe • Original 62443-3 work has been turned over to ISA 99 for their development • Zones and conduits used by TC65WG10 are applicable to ISA 99.00.04 • Requirements are testable • ISA 99WG04 challenge is to balance the detailed prescriptive specifications • Technology dependent language needs to be adjusted to ensure longer life of the specification • Language must be cast in terms of “If required by security policy, then the capability to …. is required” – most requirements become optional

  4. The need for foundational requirements • Foundational requirements can be stated that apply to any Asset Owner’s derived common reference model • PCSF seven foundational requirements • Operations centric view of requirements • The simplest set to understand and use • NIST 800-53 & INL/DHS catalog • A comprehensive treatment of requirements • A daunting task to assimilate and correlate interdependency of requirements • Suggested approach: two simultaneous teams • Start with the PCSF foundational requirements • Use the NIST and INL/DHS documents as a checklist to find missing requirements for Part 4

  5. What worked well for TC65WG10 • Common template for domains (zones & conduits) • Statement of cyber security issue addressed • Assumptions and constraints applied • Requirements addressed in another domain • Relationship to stated policy • Statement of requirement • Litmus test – it must be testable • Options to increase strength of protection (defense in depth) • Rationale or justification for requirement “This is important because ….” • Need to harmonize Part 4 statements with Parts 2 and 3 – Part 3 work needs to start

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