ISO/TS 22375:2018

TECHNICAL ISO/TS
SPECIFICATION 22375
First edition
2018-10
Security and resilience — Guidelines
for complexity assessment process
Sécurité et résilience — Lignes directrices relatives au processus
d’évaluation de la complexité
Reference number
©
ISO 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principles . 1
5 Preliminary assessment process . 2
5.1 General . 2
5.2 Mandate and commitment . 2
5.3 Needs and expectations of interested parties . 2
5.4 Embedding competence and awareness. 2
6 Planning the assessment process . 3
6.1 General . 3
6.2 Defining the scope . 3
6.3 Determining the objectives . 3
6.4 Establishing the external context . 4
6.5 Establishing the internal context . 4
6.6 Establishing resource requirements . 4
6.6.1 General. 4
6.6.2 Personnel . 4
6.6.3 Procedure . 5
6.6.4 Method . 5
6.6.5 Communication . 5
6.6.6 Documentation . 5
7 Implementing the assessment process . 6
7.1 General . 6
7.2 Assessment process . 6
8 Monitoring and review . 6
Annex A (informative) List of potential parameters that drive complexity .8
Annex B (informative) Examples of how to carry out the complexity assessment process .12
Bibliography .28
Foreword
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This document was prepared by Technical Committee ISO/TC 292, Security and resilience.
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iv © ISO 2018 – All rights reserved

Introduction
Complexity is a fundamental property of many systems. An appropriate level of complexity is required
for systems operation, but a high degree of complexity can weaken the system, particularly during
turbulent times. High system complexity could be an obstacle to the security, resilience, effectiveness
and efficiency of all organizations. As organizational systems, products, processes, technologies,
organizational structures and contracts become more complex, organizations may fail to pay sufficient
attention to the introduction and proliferation of more complex and less secure systems that then
become unsustainable and lose their integrity. Figure 1 explains where the introduction of complexity
can improve performance, but where, after it reaches certain point, it will degrade performance. Point
A is the best ratio between performance and complexity.
Figure 1 — The impact of complexity against performance
Organizational complexity cannot be increased indefinitely, however. If complexity exceeds a
manageable level, e.g. interdependencies expand to the degree that all elements are connected with
one another, the system behaviour turns chaotic. Hence, the relationship between organizational
[16]
complexity and performance is hypothesized to be inversely u-shaped, as shown in Figure 1 .
The complexity of an organization’s system is influenced by external and internal factors, often linked
to direct or indirect actions carried out by different parties.
Day-to-day managerial decisions about the organization’s activities tend to generate complexity.
For large companies with decentralized decision-making, decisions tend to be made without the
assessment of complexity cost and benefit trade-offs.
These decisions could add complexity without creating customer or competitive benefits and could
increase the organization’s vulnerability.
Moreover, the decisions taken by customers, competitors and suppliers, as well as the enactment of new
regulations, induce the organizations to adapt themselves to new scenarios. Increasing the complexity
of the external environment may induce the organization to increase the number of functional units
and this could increase functional and structural complexity of the organization.
Functional complexity is characterized by its management system and its business processes set out in
directives, procedures and reports.
Structural complexity deals with the variety of elements and relationships among the people, products
and services, and assets of the organization.
To assess the complexity of an organization’s system, it is necessary to take into account a large number
of parameters where the interactions change and develop dynamically and in a non-linear laws.
This is particularly true in the context of a turbulent and interdependent global economy, punctuated by
shocks and instabilities of increasing intensity and frequency, which can undermine the performance
and survival of any system.
High complexity is an important source of a new form of risk called “complexity-related risk” that
organizations have to address and manage if the security and resilience of its system are to be sustained.
This document aims to stimulate organizations to take into account the threat created by an excess
of complexity and to consider complexity assessment as an integral part of their plan for security
management.
vi © ISO 2018 – All rights reserved

TECHNICAL SPECIFICATION ISO/TS 22375:2018(E)
Security and resilience — Guidelines for complexity
assessment process
1 Scope
This document gives guidelines for the application of principles and a process for a complexity
assessment of an organization’s systems to improve security and resilience. A complexity assessment
process allows an organization to identify potential hidden vulnerabilities of its system and to provide
an early indication of risk resulting from complexity.
This document is generic and applicable to all sizes and types of organization systems, such as critical
assets, strategic networks, supply chains, industrial plants, community infrastructures, banks and
business companies.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 22300, Security and resilience — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 22300 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
complexity
condition of an organizational system with many diverse and autonomous but interrelated and
interdependent components or parts where those parts interact with each other and with external
elements in multiple end non-linear ways
Note 1 to entry: Complexity is the characteristic of a system where b
...