ISO/IEC 27005:2018

INTERNATIONAL ISO/IEC
STANDARD 27005
Redline version
compares Third edition to
Second edition
Information technology — Security
techniques — Information security
risk management
Technologies de l'information — Techniques de sécurité — Gestion
des risques liés à la sécurité de l'information
Reference number
ISO/IEC 27005:redline:2018(E)
©
ISO/IEC 2018

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ISO/IEC 27005:redline:2018(E)

IMPORTANT — PLEASE NOTE
This is a mark-up copy and uses the following colour coding:
Text example 1 — indicates added text (in green)
Text example 2 — indicates removed text (in red)
— indicates added graphic figure
— indicates removed graphic figure
1.x . — Heading numbers containg modifications are highlighted in yellow in
the Table of Contents
DISCLAIMER
This Redline version provides you with a quick and easy way to compare the main changes
between this edition of the standard and its previous edition. It doesn’t capture all single
changes such as punctuation but highlights the modifications providing customers with
the most valuable information. Therefore it is important to note that this Redline version is
not the official ISO standard and that the users must consult with the clean version of the
standard, which is the official standard, for implementation purposes.
COPYRIGHT PROTECTED DOCUMENT
© ISO/IEC 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO/IEC 2018 – All rights reserved

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ISO/IEC 27005:redline:2018(E)

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Structure of this International Standard document . 5
5 Background . 6
6 Overview of the information security risk management process .7
7 Context establishment .11
7.1 General considerations .11
7.2 Basic criteria .11
7.2.1 Risk management approach .11
7.2.2 Risk evaluation criteria .12
7.2.3 Impact criteria .12
7.2.4 Risk acceptance criteria .12
7.3 Scope and boundaries .13
7.4 Organization for information security risk management .14
8 Information security risk assessment .14
8.1 General description of information security risk assessment .14
8.2 Risk identification .15
8.2.1 Introduction to risk identification .15
8.2.2 Identification of assets .15
8.2.3 Identification of threats .16
8.2.4 Identification of existing controls .16
8.2.5 Identification of vulnerabilities.17
8.2.6 Identification of consequences .18
8.3 Risk analysis .18
8.3.1 Risk analysis methodologies.18
8.3.2 Assessment of consequences .20
8.3.3 Assessment of incident likelihood .21
8.3.4 Level of risk determination .21
8.4 Risk evaluation .22
9 Information security risk treatment .23
9.1 General description of risk treatment .23
9.2 Risk modification .25
9.3 Risk retention .26
9.4 Risk avoidance .26
9.5 Risk sharing .26
10 Information security risk acceptance .27
11 Information security risk communication and consultation .27
12 Information security risk monitoring and review .28
12.1 Monitoring and review of risk factors .28
12.2 Risk management monitoring, review and improvement .29
Annex A (informative) Defining the scope and boundaries of the information security risk
management process .31
Annex B (informative) Identification and valuation of assets and impact assessment .37
Annex C (informative) Examples of typical threats .53
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ISO/IEC 27005:redline:2018(E)

Annex D (informative) Vulnerabilities and methods for vulnerability assessment.58
Annex E (informative) Information security risk assessment approaches .64
Annex F (informative) Constraints for risk modification .71
Annex G (informative) Differences in definitions between ISO/IEC 27005:2008 and ISO/
IEC 27005:2011 .75
Bibliography .84
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ISO/IEC 27005:redline:2018(E)

Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
members of ISO or IEC participate in the development of International Standards through technical
committees established by the respective organization to deal with particular fields of technical
activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international
organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the
work. In the field of information technology, ISO and IEC have established a joint technical committee,
ISO/IEC JTC 1.
International Standards areThe procedures used to develop this document and those intended for
its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different
approval criteria needed for the different types of document should be noted. This document was
drafted in accordance with the rules given ineditorial rules of the ISO/IEC Directives, Part 2 (see www
.iso .org/directives).
The main task of the joint technical committee is to prepare International Standards. Draft International
Standards adopted by the joint technical committee are circulated to national bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the national bodies
casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject
of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent
rights. Details of any patent rights identified during the development of the document will be in the
Introduction and/or on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www .iso .org/iso/foreword .html.
ISO/IEC 27005This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information
technology, Subcommittee SC 27, IT Security techniques.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
This secondthird edition cancels and replaces the firstsecond edition (ISO/IEC 27005:20082011) which
has been technically revised. The main changes from the previous edition are as follows:
— all direct references to the ISO/IEC 27001:2005 have been removed;
— clear information has been added that this document does not contain direct guidance on the
implementation of the ISMS requirements specified in ISO/IEC 27001 (see Introduction);
— ISO/IEC 27001:2005 has been removed from Clause 2;
— ISO/IEC 27001 has been added to the Bibliography;
— Annex G and all references to it have been removed;
— editorial changes have been made accordingly.
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ISO/IEC 27005:redline:2018(E)

Introduction
This International Standarddocument provides guidelines for information security risk management
in an organization, supporting in particular the requirements of an information security management
(ISMS) according to ISO/IEC 27001. However, this International Standarddocument does not provide
any specific method for information security risk management. It is up to the organization to define their
approach to risk management, depending for example on the scope of the ISMSan information security
management system (ISMS), context of risk management, or industry sector. A number of existing
methodologies can be used under the framework described in this International Standarddocument to
implement the requirements of an ISMS. This document is based on the asset, threat and vulnerability
risk identification method that is no longer required by ISO/IEC 27001. There are some other approaches
that can be used.
This document does not contain direct guidance on the implementation of the ISMS requirements given
in ISO/IEC 27001.
This International Standarddocument is relevant to managers and staff concerned with information
security risk management within an organization and, where appropriate, external parties supporting
such activities.
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INTERNATIONAL STANDARD ISO/IEC 27005:redline:2018(E)
Information technology — Security techniques —
Information security risk management
1 Scope
This International Standarddocument provides guidelines for information security risk management.
This International Standarddocument supports the general concepts specified in ISO/IEC 27001 and is
designed to assist the satisfactory implementation of information security based on a risk management
approach.
Knowledge of the concepts, models, processes and terminologies described in ISO/IEC 27001 and ISO/
IEC 27002 is important for a complete understanding of this International Standarddocument.
This International Standarddocument is applicable to all types of organizations (e.g. commercial
enterprises, government agencies, non-profit organizations) which intend to manage risks that couldcan
compromise the organization’s information security.
2 Normative references
The following referenced documents are indispensable for the application ofreferred 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/IEC 27000, Information technology — Security techniques — Information security management
systems — Overview and vocabulary
ISO/IEC 27001:2005, Information technology — Security techniques — Information security management
systems — Requirements
ISO/IEC 27000, Information technology — Security techniques — Information security management
systems — Overview and vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 27000 and the
following apply.
NOTE Differences in definitions between ISO/IEC 27005:2008 and this International Standard are shown in
Annex G.
3.1
consequence
outcome of an event (3.3) affecting objectives
[SOURCE: ISO Guide 73:2009]
Note 1 to entry: An event can lead to a range of consequences.
Note 2 to entry: A consequence can be certain or uncertain and in the context of information security is usually
negative.
Note 3 to entry: Consequences can be expressed qualitatively or quantitatively.
Note 4 to entry: Initial consequences can escalate through knock-on effects.
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ISO/IEC 27005:redline:2018(E)

3.2
control
measure that is modifying risk (3.9)
[SOURCE: ISO Guide 73:2009]
Note 1 to entry: Controls for information security include any process, policy, procedure, guideline, practice or
organizational structure, which can be administrative, technical, management, or legal in nature which modify
information security risk.
Note 2 to entry: Controls may not always exert the intended or assumed modifying effect.
Note 3 to entry: Control is also used as a synonym for safeguard or countermeasure.
3.3
event
occurrence or change of a particular set of circumstances
[SOURCE: ISO Guide 73:2009]
Note 1 to entry: An event can be one or more occurrences, and can have several causes.
Note 2 to entry: An event can consist of something not happening.
Note 3 to entry: An event can sometimes be referred to as an “incident” or “accident”.
3.4
external context
external environment in which the organization seeks to achieve its objectives
[SOURCE: ISO Guide 73:2009]
Note 1 to entry: External context can include:
— the cultural, social, political, legal, regulatory, financial, technological, economic, natural and competitive
environment, whether international, national, regional or local;
— key drivers and trends having impact on the objectives of the organization; and
— relationships with, and perceptions and values of, external stakeholders.
3.5
internal context
internal environment in which the organization seeks to achieve its objectives
[SOURCE: ISO Guide 73:2009]
Note 1 to entry: Internal context can include:
— governance, organizational structure, roles and accountabilities;
— policies, objectives, and the strategies that are in place to achieve them;
— the capabilities, understood in terms of resources and knowledge (e.g. capital, time, people, processes,
systems and technologies);
— information systems, information flows and decision-making processes (both formal and informal);
— relationships with, and perceptions and values of, internal stakeholders;
— the organization's culture;
— standards, guidelines and models adopted by the organization; and
— form and extent of contractual relationships.
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ISO/IEC 27005:redline:2018(E)

3.6
level of risk
magnitude of a risk (3.9), expressed in terms of the combination of consequences (3.1) and their
likelihood (3.7)
[SOURCE: ISO Guide 73:2009]
3.7
likelihood
chance of something happening
[SOURCE: ISO Guide 73:2009]
Note 1 to entry: In risk management terminology, the word “likelihood” is used to refer to the chance of something
happening, whether defined, measured or determined objectively or subjectively, qualitatively or quantitatively,
and described using general terms or mathematically (such as a probability or a frequency over a given time
period).
Note 2 to entry: The English term “likelihood” does not have a direct equivalent in some languages; instead, the
equivalent of the term “probability” is often used. However, in English, “probability” is often narrowly interpreted
as a mathematical term. Therefore, in risk management terminology, “likelihood” is used with the intent that it
should have the same broad interpretation as the term “probability” has in many languages other than English.
3.8
residual risk
risk (3.9) remaining after risk treatment (3.17)
[SOURCE: ISO Guide 73:2009]
Note 1 to entry: Residual risk can contain unidentified risk.
Note 2 to entry: Residual risk can also be known as “retained risk”.
3.9
risk
effect of uncertainty on objectives
[SOURCE: ISO Guide 73:2009]
Note 1 to entry: An effect is a deviation from the expected — positive and/or negative.
Note 2 to entry: Objectives can have different aspects (such as financial, health and safety, information security,
and environmental goals) and can apply at different levels (such as strategic, organization-wide, project, product
and process).
Note 3 to entry: Risk is often characterized by reference to potential events (3.3) and consequences (3.1), or a
combination of these.
Note 4 to entry: Information security risk is often expressed in terms of a combination of the consequences of an
information security event and the associated likelihood (3.9) of occurrence.
Note 5 to entry: Uncertainty is the state, even partial, of deficiency of information related to, understanding or
knowledge of, an event, its consequence, or likelihood.
Note 6 to entry: Information security risk is associated with the potential that threats will exploit vulnerabilities
of an information asset or group of information assets and thereby cause harm to an organization.
3.10
risk analysis
process to comprehend the nature of risk and to determine the level of risk (3.6)
[SOURCE: ISO Guide 73:2009]
Note 1 to entry: Risk analysis provides the basis for risk evaluation and decisions about risk treatment.
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ISO/IEC 27005:redline:2018(E)

Note 2 to entry: Risk analysis includes risk estimation.
3.11
risk assessment
overall process of risk identification (3.15), risk analysis (3.10) and risk evaluation (3.14)
[SOURCE: ISO Guide 73:2009]
3.12
risk communication and consultation
continual and iterative processes that an organization conducts to provide, share or obtain information,
and to engage in dialogue with stakeholders (3.18) regarding the management of risk (3.9)
[SOURCE: ISO Guide 73:2009]
Note 1 to entry: The information can relate to the existence, nature, form, likelihood, significance, evaluation,
acceptability and treatment of risk.
Note 2 to entry: Consultation is a two-way process of informed communication between an organization and its
stakeholders on an issue prior to making a decision or determining a direction on that issue. Consultation is:
— a process which impacts on a decision through influence rather than power; and
— an input to decision making, not joint decision making.
3.13
risk criteria
terms of reference against which the significance of a risk (3.9) is evaluated
[SOURCE: ISO Guide 73:2009]
Note 1 to entry: Risk criteria are based on organizational objectives, and external and internal context.
Note 2 to entry: Risk criteria can be derived from standards, laws, policies and other requirements.
3.14
risk evaluation
process of comparing the results of risk analysis (3.10) with risk criteria (3.13) to determine whether
the risk and/or its magnitude is acceptable or tolerable
[SOURCE: ISO Guide 73:2009]
Note 1 to entry: Risk evaluation assists in the decision about risk treatment.
3.15
risk identification
process of finding, recognizing and describing risks
[SOURCE: ISO Guide 73:2009]
Note 1 to entry: Risk identification involves the identification of risk sources, events, their causes and their
potential consequences.
Note 2 to entry: Risk identification can involve historical data, theoretical analysis, informed and expert opinions,
and stakeholders’ needs.
3.16
risk management
coordinated activities to direct and control an organization with regard to risk
[SOURCE: ISO Guide 73:2009]
Note 1 to entry: This International Standard uses the term ‘process’ to describe risk management overall. The
elements within the risk management process are termed ‘activities’
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3.17
risk treatment
process to modify risk
[SOURCE: ISO Guide 73:2009]
Note 1 to entry: Risk treatment can involve:
— avoiding the risk by deciding not to start or continue with the activity that gives rise to the risk;
— taking or increasing risk in order to pursue an opportunity;
— removing the risk source;
— changing the likelihood;
— changing the consequences;
— sharing the risk with another party or parties (including contracts and risk financing); and
— retaining the risk by informed choice.
Note 2 to entry: Risk treatments that deal with negative consequences are sometimes referred to as “risk
mitigation”, “risk elimination”, “risk prevention” and “risk reduction”.
Note 3 to entry: Risk treatment can create new risks or modify existing risks.
3.18
stakeholder
person or organization that can affect, be affected by, or perceive themselves to be affected by a decision
or activity
[SOURCE: ISO Guide 73:2009]
Note 1 to entry: decision maker can be a stakeholder.
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/
4 Structure of this International Standard document
This International Standarddocument contains the description of the information security risk
management process and its activities.
The background information is provided in Clause 5.
A general overview of the information security risk management process is given in Clause 6.
All information security risk management activities as presented in Clause 6 are subsequently
described in the following clauses:
• — context establishment in Clause 7,;
• — risk assessment in Clause 8,;
• — risk treatment in Clause 9,;
• — risk acceptance in Clause Clause 10,;
• — risk communication in Clause 11,;
• — risk monitoring and review in Clause 12.
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ISO/IEC 27005:redline:2018(E)

Additional information for information security risk management activities is presented in the
annexes. The context establishment is supported by Annex A (Defining the scope and boundaries of
the information security risk management process). Identification and valuation of assets and impact
assessments are discussed in Annex B. Annex C gives examples of typical threats and Annex D discusses
vulnerabilities and methods for vulnerability assessment. Examples of information security risk
assessment approaches are presented in Annex E.
Constraints for risk modification are presented in Annex F.
Differences in definitions between ISO/IEC 27005:2008 and ISO/IEC 27005:2011 are shown in Annex G.
All risk management activities as presented from Clause 7 to Clause 12 are structured as follows:
Input: Identifies any required information to perform the activity.
Action: Describes the activity.
Implementation guidance: Provides guidance on performing the action. Some of this guidance may not
be suitable in all cases and so other ways of performing the action may be more appropriate.
Output: Identifies any information derived after performing the activity.
5 Background
A systematic approach to information security risk management is necessary to identify organizational
needs regarding information security requirements and to create an effective information security
management system (I
...

INTERNATIONAL ISO/IEC
STANDARD 27005
Third edition
2018-07
Information technology — Security
techniques — Information security
risk management
Technologies de l'information — Techniques de sécurité — Gestion
des risques liés à la sécurité de l'information
Reference number
ISO/IEC 27005:2018(E)
©
ISO/IEC 2018

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ISO/IEC 27005:2018(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO/IEC 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO/IEC 2018 – All rights reserved

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ISO/IEC 27005:2018(E)

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Structure of this document . 1
5 Background . 2
6 Overview of the information security risk management process .3
7 Context establishment . 5
7.1 General considerations . 5
7.2 Basic criteria . 6
7.2.1 Risk management approach . 6
7.2.2 Risk evaluation criteria . 6
7.2.3 Impact criteria . 6
7.2.4 Risk acceptance criteria . 7
7.3 Scope and boundaries . 7
7.4 Organization for information security risk management . 8
8 Information security risk assessment . 8
8.1 General description of information security risk assessment . 8
8.2 Risk identification . 9
8.2.1 Introduction to risk identification . 9
8.2.2 Identification of assets . 9
8.2.3 Identification of threats .10
8.2.4 Identification of existing controls .10
8.2.5 Identification of vulnerabilities.11
8.2.6 Identification of consequences .12
8.3 Risk analysis .12
8.3.1 Risk analysis methodologies.12
8.3.2 Assessment of consequences .13
8.3.3 Assessment of incident likelihood .14
8.3.4 Level of risk determination .15
8.4 Risk evaluation .15
9 Information security risk treatment .16
9.1 General description of risk treatment .16
9.2 Risk modification .18
9.3 Risk retention .19
9.4 Risk avoidance .19
9.5 Risk sharing .19
10 Information security risk acceptance .20
11 Information security risk communication and consultation .20
12 Information security risk monitoring and review .21
12.1 Monitoring and review of risk factors .21
12.2 Risk management monitoring, review and improvement .22
Annex A (informative) Defining the scope and boundaries of the information security risk
management process .24
Annex B (informative) Identification and valuation of assets and impact assessment .28
Annex C (informative) Examples of typical threats .37
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ISO/IEC 27005:2018(E)

Annex D (informative) Vulnerabilities and methods for vulnerability assessment.41
Annex E (informative) Information security risk assessment approaches .45
Annex F (informative) Constraints for risk modification .51
Bibliography .53
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ISO/IEC 27005:2018(E)

Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
members of ISO or IEC participate in the development of International Standards through technical
committees established by the respective organization to deal with particular fields of technical
activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international
organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the
work. In the field of information technology, ISO and IEC have established a joint technical committee,
ISO/IEC JTC 1.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for
the different types of document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject
of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent
rights. Details of any patent rights identified during the development of the document will be in the
Introduction and/or on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www .iso .org/iso/foreword .html.
This document was prepared by Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 27, IT Security techniques.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
This third edition cancels and replaces the second edition (ISO/IEC 27005:2011) which has been
technically revised. The main changes from the previous edition are as follows:
— all direct references to the ISO/IEC 27001:2005 have been removed;
— clear information has been added that this document does not contain direct guidance on the
implementation of the ISMS requirements specified in ISO/IEC 27001 (see Introduction);
— ISO/IEC 27001:2005 has been removed from Clause 2;
— ISO/IEC 27001 has been added to the Bibliography;
— Annex G and all references to it have been removed;
— editorial changes have been made accordingly.
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ISO/IEC 27005:2018(E)

Introduction
This document provides guidelines for information security risk management in an organization.
However, this document does not provide any specific method for information security risk management.
It is up to the organization to define their approach to risk management, depending for example on
the scope of an information security management system (ISMS), context of risk management, or
industry sector. A number of existing methodologies can be used under the framework described in
this document to implement the requirements of an ISMS. This document is based on the asset, threat
and vulnerability risk identification method that is no longer required by ISO/IEC 27001. There are
some other approaches that can be used.
This document does not contain direct guidance on the implementation of the ISMS requirements given
in ISO/IEC 27001.
This document is relevant to managers and staff concerned with information security risk management
within an organization and, where appropriate, external parties supporting such activities.
vi © ISO/IEC 2018 – All rights reserved

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INTERNATIONAL STANDARD ISO/IEC 27005:2018(E)
Information technology — Security techniques —
Information security risk management
1 Scope
This document provides guidelines for information security risk management.
This document supports the general concepts specified in ISO/IEC 27001 and is designed to assist the
satisfactory implementation of information security based on a risk management approach.
Knowledge of the concepts, models, processes and terminologies described in ISO/IEC 27001 and ISO/
IEC 27002 is important for a complete understanding of this document.
This document is applicable to all types of organizations (e.g. commercial enterprises, government
agencies, non-profit organizations) which intend to manage risks that can compromise the organization’s
information security.
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/IEC 27000, Information technology — Security techniques — Information security management
systems — Overview and vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 27000 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/
4 Structure of this document
This document contains the description of the information security risk management process and its
activities.
The background information is provided in Clause 5.
A general overview of the information security risk management process is given in Clause 6.
All information security risk management activities as presented in Clause 6 are subsequently
described in the following clauses:
— context establishment in Clause 7;
— risk assessment in Clause 8;
— risk treatment in Clause 9;
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ISO/IEC 27005:2018(E)

— risk acceptance in Clause 10;
— risk communication in Clause 11;
— risk monitoring and review in Clause 12.
Additional information for information security risk management activities is presented in the
annexes. The context establishment is supported by Annex A (Defining the scope and boundaries of
the information security risk management process). Identification and valuation of assets and impact
assessments are discussed in Annex B. Annex C gives examples of typical threats and Annex D discusses
vulnerabilities and methods for vulnerability assessment. Examples of information security risk
assessment approaches are presented in Annex E.
Constraints for risk modification are presented in Annex F.
All risk management activities as presented from Clause 7 to Clause 12 are structured as follows:
Input: Identifies any required information to perform the activity.
Action: Describes the activity.
Implementation guidance: Provides guidance on performing the action. Some of this guidance may not
be suitable in all cases and so other ways of performing the action may be more appropriate.
Output: Identifies any information derived after performing the activity.
5 Background
A systematic approach to information security risk management is necessary to identify organizational
needs regarding information security requirements and to create an effective information security
management system (ISMS). This approach should be suitable for the organization’s environment
and, in particular, should be aligned with overall enterprise risk management. Security efforts should
address risks in an effective and timely manner where and when they are needed. Information security
risk management should be an integral part of all information security management activities and
should be applied both to the implementation and the ongoing operation of an ISMS.
Information security risk management should be a continual process. The process should establish
the external and internal context, assess the risks and treat the risks using a risk treatment plan to
implement the recommendations and decisions. Risk management analyses what can happen and what
the possible consequences can be, before deciding what should be done and when, to reduce the risk to
an acceptable level.
Information security risk management should contribute to the following:
— risks being identified;
— risks being assessed in terms of their consequences to the business and the likelihood of their
occurrence;
— the likelihood and consequences of these risks being communicated and understood;
— priority order for risk treatment being established;
— priority for actions to reduce risks occurring;
— stakeholders being involved when risk management decisions are made and kept informed of the
risk management status;
— effectiveness of risk treatment monitoring;
— risks and the risk management process being monitored and reviewed regularly;
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— information being captured to improve the risk management approach;
— managers and staff being educated about the risks and the actions taken to mitigate them.
The information security risk management process can be applied to the organization as a whole, any
discrete part of the organization (e.g. a department, a physical location, a service), any information
system, existing or planned or particular aspects of control (e.g. business continuity planning).
6 Overview of the information security risk management process
A high level view of the risk management process is specified in ISO 31000 and shown in Figure 1.
Figure 1 — The risk management process
Figure 2 shows how this document applies this risk management process.
The information security risk management process consists of context establishment (Clause 7), risk
assessment (Clause 8), risk treatment (Clause 9), risk acceptance (Clause 10), risk communication and
consultation (Clause 11), and risk monitoring and review (Clause 12).
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Figure 2 — Illustration of an information security risk management process
As Figure 2 illustrates, the information security risk management process can be iterative for risk
assessment and/or risk treatment activities. An iterative approach to conducting risk assessment can
increase depth and detail of the assessment at each iteration. The iterative approach provides a good
balance between minimizing the time and effort spent in identifying controls, while still ensuring that
high risks are appropriately assessed.
The context is established first. Then, a risk assessment is conducted. If this provides sufficient
information to effectively determine the actions required to modify the risks to an acceptable level,
then the task is complete and the risk treatment follows. If the information is insufficient, another
iteration of the risk assessment with revised context (e.g. risk evaluation criteria, risk acceptance
criteria or impact criteria) is conducted, possibly on limited parts of the total scope (see Figure 2, Risk
Decision Point 1).
The effectiveness of the risk treatment depends on the results of the risk assessment.
Note that risk treatment involves a cyclical process of:
— assessing a risk treatment;
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— deciding whether residual risk levels are acceptable;
— generating a new risk treatment if risk levels are not acceptable; and
— assessing the effectiveness of that treatment.
It is possible that the risk treatment does not immediately lead to an acceptable level of residual risk.
In this situation, another iteration of the risk assessment with changed context parameters (e.g. risk
assessment, risk acceptance or impact criteria), if necessary, can be required, followed by further risk
treatment (see Figure 2, Risk Decision Point 2).
The risk acceptance activity has to ensure residual risks are explicitly accepted by the managers of
the organization. This is especially important in a situation where the implementation of controls is
omitted or postponed, e.g. due to cost.
During the whole information security risk management process, it is important that risks and their
treatment are communicated to the appropriate managers and operational staff. Even before the
treatment of the risks, information about identified risks can be very valuable to manage incidents and
can help to reduce potential damage. Awareness by managers and staff of the risks, the nature of the
controls in place to mitigate the risks and the areas of concern to the organization assist in dealing with
incidents and unexpected events in the most effective manner. The detailed results of every activity
of the information security risk management process and from the two risk decision points should be
documented.
ISO/IEC 27001 specifies that the controls implemented within the scope, boundaries and context of
the ISMS need to be risk-based. The application of an information security risk management process
can satisfy this requirement. There are many approaches by which controls can be determined to
implement the risk treatment options chosen.
The organization should establish, implement and maintain a procedure to identify the legal
requirements applicable to:
— the selection of criteria for risk evaluation (7.2.2), risk impact (7.2.3) and risk acceptance (7.2.4);
— the definition of the scope and boundaries of information security risk management (7.3 and A.2);
— risk evaluation (8.4);
— risk treatment of (9.1) and the implementation of risk reduction plans (9.2 and Annex F);
— the monitoring, review and improvement of risk management (12.2);
— asset identification (B.1.3) and asset valuation (B.2.3); and
— risk estimation (see examples in E.2.1).
7 Context establishment
7.1 General considerations
Input: All information about the organization relevant to the information security risk management
context establishment.
Action: The external and internal context for information security risk management should be
established, which involves setting the basic criteria necessary for information security risk
management (7.2), defining the scope and boundaries (7.3), and establishing an appropriate
organization operating the information security risk management (7.4).
Implementation guidance:
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It is essential to determine the purpose of the information security risk management as this affects the
overall process and the context establishment in particular. This purpose can be:
— supporting an ISMS;
— legal compliance and evidence of due diligence;
— preparation of a business continuity plan;
— preparation of an incident response plan; and
— description of the information security requirements for a product, a service or a mechanism.
Implementation guidance for context establishment elements needed to support an ISMS is further
discussed in 7.2, 7.3 and 7.4 below.
Output: The specification of basic criteria, the scope and boundaries, and the organization for the
information security risk management process.
7.2 Basic criteria
7.2.1 Risk management approach
Depending on the scope and objectives of the risk management, different approaches can be applied.
The approach can also be different for each iteration.
An appropriate risk management approach should be selected or developed that addresses basic criteria
such as: risk evaluation criteria, impact criteria, risk acceptance criteria.
Additionally, the organization should assess whether necessary resources are available to:
— perform risk assessment and establish a risk treatment plan;
— define and implement policies and procedures, including implementation of the controls selected;
— monitor controls; and
— monitor the information security risk management process.
7.2.2 Risk evaluation criteria
Risk evaluation criteria should be developed for evaluating the organization's information security risk
considering the following:
— the strategic value of the business information process;
— the criticality of the information assets involved;
— operational and business importance of availability, confidentiality and integrity;
— stakeholders’ expectations and perceptions, and negative consequences for goodwill and reputation;
Additionally, risk evaluation criteria can be used to specify priorities for risk treatment.
7.2.3 Impact criteria
NOTE ISO 31000 uses a concept of “consequence criteria” instead of “impact criteria”.
Impact criteria should be developed and specified in terms of the degree of damage or costs to the
organization caused by an information security event considering the following:
— level of classification of the impacted information asset;
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— breaches of information security (e.g. loss of confidentiality, integrity and availability);
— impaired operations (internal or third parties);
— loss of business and financial value;
— disruption of plans and deadlines;
— damage of reputation;
7.2.4 Risk acceptance criteria
Risk acceptance criteria should be developed and specified. Risk acceptance criteria often depend on
the organization's policies, goals, objectives and the interests of stakeholders.
An organization should define its own scales for levels of risk acceptance. The following should be
considered during development:
— risk acceptance criteria can include multiple thresholds, with a desired target level of risk, but
provision for senior managers to accept risks above this level under defined circumstances;
— risk acceptance criteria can be expressed as the ratio of estimated profit (or other business benefit)
to the estimated risk;
— different risk acceptance criteria can apply to different classes of risk;
— risk acceptance criteria can include requirements for future additional treatment, e.g. a risk can
be accepted if there is approval and commitment to take action to reduce it to an acceptable level
within a defined time period.
Risk acceptance criteria can differ according to how long the risk is expected to exist, e.g. the risk
can be associated with a temporary or short-term activity. Risk acceptance criteria should be set up
considering the following:
— business criteria;
— operations;
— technology;
— finance;
— social and humanitarian factors.
More information can be found in Annex A.
7.3 Scope and boundaries
The organization should define the scope and boundaries of information security risk management.
The scope of the inf
...

NORME ISO/IEC
INTERNATIONALE 27005
Troisième édition
2018-07
Technologies de l'information —
Techniques de sécurité — Gestion
des risques liés à la sécurité de
l'information
Information technology — Security techniques — Information
security risk management
Numéro de référence
ISO/IEC 27005:2018(F)
©
ISO/IEC 2018

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ISO/IEC 27005:2018(F)

DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO/IEC 2018
Tous droits réservés. Sauf prescription différente ou nécessité dans le contexte de sa mise en œuvre, aucune partie de cette
publication ne peut être reproduite ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique,
y compris la photocopie, ou la diffusion sur l’internet ou sur un intranet, sans autorisation écrite préalable. Une autorisation peut
être demandée à l’ISO à l’adresse ci-après ou au comité membre de l’ISO dans le pays du demandeur.
ISO copyright office
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Publié en Suisse
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Sommaire Page
Avant-propos .v
Introduction .vi
1 Domaine d'application . 1
2 Références normatives . 1
3 Termes et définitions . 1
4 Structure du présent document . 1
5 Contexte . 2
6 Présentation générale du processus de gestion des risques en sécurité de l'information .3
7 Établissement du contexte . 6
7.1 Considérations générales . 6
7.2 Critères de base . 6
7.2.1 Approche de gestion des risques . 6
7.2.2 Critères d'évaluation du risque . 7
7.2.3 Critères d'impact . 7
7.2.4 Critères d'acceptation des risques . 7
7.3 Domaine d'application et limites . 8
7.4 Organisation de la gestion des risques en sécurité de l'information . 9
8 Appréciation des risques en sécurité de l'information . 9
8.1 Description générale de l'appréciation des risques en sécurité de l'information . 9
8.2 Identification des risques .10
8.2.1 Introduction à l'identification des risques .10
8.2.2 Identification des actifs .10
8.2.3 Identification des menaces .11
8.2.4 Identification des mesures de sécurité existantes .11
8.2.5 Identification des vulnérabilités .12
8.2.6 Identification des conséquences .13
8.3 Analyse des risques .14
8.3.1 Méthodologies d'analyse des risques .14
8.3.2 Appréciation des conséquences .15
8.3.3 Appréciation de la vraisemblance d'un incident .16
8.3.4 Estimation du niveau des risques .16
8.4 Évaluation des risques.17
9 Traitement des risques en sécurité de l'information .17
9.1 Description générale du traitement des risques.17
9.2 Réduction du risque .19
9.3 Maintien des risques .20
9.4 Refus des risques .21
9.5 Partage des risques .21
10 Acceptation des risques en sécurité de l'information .21
11 Communication et concertation relatives aux risques en sécurité de l'information .22
12 Surveillance et réexamen des risques en sécurité de l'information .23
12.1 Surveillance et réexamen des facteurs de risque .23
12.2 Surveillance, réexamen et amélioration de la gestion des risques .24
Annexe A (informative) Définition du domaine d'application et des limites du processus de
gestion des risques en sécurité de l'information .26
Annexe B (informative) Identification et valorisation des actifs et appréciation des impacts.31
Annexe C (informative) Exemples de menaces types .40
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Annexe D (informative) Vulnérabilités et méthodes d'appréciation des vulnérabilités .44
Annexe E (informative) Approches d'appréciation des risques en sécurité de l'information .49
Annexe F (informative) Contraintes liées à la réduction du risque .55
Bibliographie .57
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Avant-propos
L'ISO (Organisation internationale de normalisation) et l’IEC (Commission électrotechnique
internationale) forment le système spécialisé de la normalisation mondiale. Les organismes
nationaux membres de l'ISO ou de l’IEC participent au développement de Normes internationales
par l'intermédiaire des comités techniques créés par l'organisation concernée afin de s'occuper des
domaines particuliers de l'activité technique. Les comités techniques de l'ISO et de l’IEC collaborent
dans des domaines d'intérêt commun. D'autres organisations internationales, gouvernementales et non
gouvernementales, en liaison avec l'ISO et l’IEC, participent également aux travaux. Dans le domaine
des technologies de l'information, l'ISO et l’IEC ont créé un comité technique mixte, l'ISO/IEC JTC 1.
Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont
décrites dans les Directives ISO/IEC, Partie 1. Il convient, en particulier, de prendre note des différents
critères d'approbation requis pour les différents types de documents ISO. Le présent document a été
rédigé conformément aux règles de rédaction données dans les Directives ISO/IEC, Partie 2 (voir www
.iso .org/directives).
L'attention est attirée sur le fait que certains des éléments du présent document peuvent faire l'objet
de droits de propriété intellectuelle ou de droits analogues. L'ISO et l’IEC ne sauraient être tenues pour
responsables de ne pas avoir identifié de tels droits de propriété et averti de leur existence. Les détails
concernant les références aux droits de propriété intellectuelle ou autres droits analogues identifiés
lors de l'élaboration du document sont indiqués dans l'Introduction et/ou dans la liste des déclarations
de brevets reçues par l'ISO (voir www .iso .org/brevets).
Les appellations commerciales éventuellement mentionnées dans le présent document sont données
pour information, par souci de commodité, à l’intention des utilisateurs et ne sauraient constituer un
engagement.
Pour une explication de la nature volontaire des normes, la signification des termes et expressions
spécifiques de l'ISO liés à l'évaluation de la conformité, ou pour toute information au sujet de l'adhésion
de l'ISO aux principes de l’Organisation mondiale du commerce (OMC) concernant les obstacles
techniques au commerce (OTC), voir www .iso .org/avant -propos.
Le présent document a été élaboré par le comité technique ISO/IEC JTC 1, Technologies de l'information,
sous-comité SC 27, Techniques de sécurité des technologies de l'information.
Il convient que l’utilisateur adresse tout retour d’information ou toute question concernant le présent
document à l’organisme national de normalisation de son pays. Une liste exhaustive desdits organismes
se trouve à l’adresse www .iso .org/fr/members .html.
Cette troisième édition annule et remplace la deuxième édition (ISO/IEC 27005:2011) qui a fait l'objet
d'une révision technique.
Les principales modifications par rapport à l’édition précédente sont les suivantes:
— toutes les références directes à l’ISO/IEC 27001:2005 ont été supprimées;
— une information claire a été ajoutée, stipulant que le présent document ne contient pas de
préconisations directes concernant la mise en œuvre des exigences du SMSI spécifiées dans l’ISO/
IEC 27001 (voir Introduction);
— l’ISO/IEC 27001:2005 a été supprimée de l’Article 2;
— l’ISO/IEC 27001 a été ajoutée à la Bibliographie;
— l’Annexe G et toutes les références à cette Annexe ont été supprimées;
— des modifications éditoriales ont été effectuées en conséquence.
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Introduction
Le présent document contient des lignes directrices relatives à la gestion des risques en sécurité de
l'information dans un organisme. Cependant, le présent document ne fournit aucune méthodologie
spécifique à la gestion des risques en sécurité de l'information. Il est du ressort de chaque organisme de
définir son approche de la gestion des risques, en fonction, par exemple, du périmètre d’un système de
management de la sécurité de l’information (SMSI), de ce qui existe dans l'organisme dans le domaine de
la gestion des risques, ou encore de son secteur industriel. Plusieurs méthodologies existantes peuvent
être utilisées en cohérence avec le cadre décrit dans le présent document pour appliquer les exigences
du SMSI. Le présent document est fondé sur la méthode d’identification des risques liés à des actifs, des
menaces et des vulnérabilités, qui n’est plus exigée par l’ISO/IEC 27001; il existe d’autres approches qui
peuvent être utilisées.
Le présent document ne contient pas de préconisations directes concernant la mise en œuvre des
exigences du SMSI spécifiées dans l’ISO/IEC 27001.
Le présent document s'adresse aux responsables et aux personnels concernés par la gestion des risques
en sécurité de l'information au sein d'un organisme et, le cas échéant, aux tiers prenant part à ces
activités.
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NORME INTERNATIONALE ISO/IEC 27005:2018(F)
Technologies de l'information — Techniques de sécurité —
Gestion des risques liés à la sécurité de l'information
1 Domaine d'application
Le présent document contient des lignes directrices relatives à la gestion des risques en sécurité de
l'information.
Le présent document appuie les concepts généraux énoncés dans l'ISO/IEC 27001; il est conçu pour
aider à la mise en place de la sécurité de l'information basée sur une approche de gestion des risques.
Il est important de connaître les concepts, les modèles, les processus et les terminologies décrites dans
l'ISO/IEC 27001 et l'ISO/IEC 27002 afin de bien comprendre le présent document.
Le présent document est applicable à tous types d'organismes (par exemple les entreprises
commerciales, les agences gouvernementales, les organisations à but non lucratif) qui ont l'intention de
gérer des risques susceptibles de compromettre la sécurité des informations de l'organisme.
2 Références normatives
Les documents suivants cités dans le texte constituent, pour tout ou partie de leur contenu, des
exigences du présent document. Pour les références datées, seule l'édition citée s'applique. Pour les
références non datées, la dernière édition du document de référence s'applique (y compris les éventuels
amendements).
ISO/IEC 27000, Technologies de l'information — Techniques de sécurité — Systèmes de management de la
sécurité de l'information — Vue d'ensemble et vocabulaire
3 Termes et définitions
Pour les besoins du présent document, les termes et les définitions de l'ISO/IEC 27000 s'appliquent.
L’ISO et l’IEC tiennent à jour des bases de données terminologiques destinées à être utilisées en
normalisation, consultables aux adresses suivantes:
— ISO Online browsing platform: disponible à l’adresse https: //www .iso .org/obp
— IEC Electropedia: disponible à l’adresse http: //www .electropedia .org/
4 Structure du présent document
Le présent document contient la description du processus de gestion des risques en sécurité de
l'information et la description de ses activités.
Les informations générales sont fournies dans l'Article 5.
Un aperçu général du processus de gestion des risques en sécurité de l'information est donné
dans l'Article 6.
Toutes les activités liées à la gestion des risques en sécurité de l'information, telles que présentées
dans l'Article 6, sont ensuite décrites dans les articles suivants:
— établissement du contexte dans l'Article 7;
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— appréciation des risques dans l'Article 8;
— traitement des risques dans l'Article 9;
— acceptation des risques dans l'Article 10;
— communication et concertation relatives aux risques dans l'Article 11;
— surveillance et réexamen des risques dans l'Article 12.
Des informations supplémentaires relatives aux activités de gestion des risques en sécurité de
l'information sont présentées dans les annexes. L'établissement du contexte est abordé dans l'Annexe A
(Définition du domaine d'application et des limites du processus de gestion des risques en sécurité de
l'information). L'identification, la valorisation des actifs et l'appréciation des impacts sont traitées dans
l'Annexe B. L'Annexe C donne des exemples de menaces type et l'Annexe D traite des vulnérabilités et
des méthodes d’appréciation des vulnérabilités. Des exemples d'approches relatives à l'appréciation des
risques en sécurité de l'information sont présentés dans l'Annexe E.
Les contraintes liées à la réduction du risque sont traitées dans l'Annexe F.
Toutes les activités liées à la gestion des risques, présentées dans les Articles 7 à 12, sont structurées de
la manière suivante:
Élément(s) d'entrée: Identifie toute information requise pour réaliser l'activité.
Action: Décrit l'activité.
Préconisations de mise en œuvre: Propose des préconisations pour réaliser l'action. Il se peut que
certaines préconisations ne soient pas adaptées à tous les cas, et que d'autres solutions pour réaliser
l'action s'avèrent préférables.
Élément(s) de sortie: Identifie toute information obtenue après la réalisation de l'activité.
5 Contexte
Une approche systématique de la gestion des risques en sécurité de l'information est nécessaire pour
identifier les besoins organisationnels concernant les exigences en matière de sécurité de l'information,
et pour créer un système de management de la sécurité de l'information (SMSI) efficace. Il convient
que cette approche soit adaptée à l'environnement de l'organisme et soit notamment alignée sur la
démarche générale de gestion des risques de l'entreprise. Il convient que les efforts effectués en matière
de sécurité adressent les risques de manière efficace et opportune quand et lorsque cela est nécessaire.
Il convient que la gestion des risques en sécurité de l'information fasse partie intégrante de l'ensemble
des activités de management de la sécurité de l'information et qu'elle s'applique à la fois à la mise en
œuvre et au fonctionnement d'un SMSI.
Il convient que la gestion des risques en sécurité de l'information soit un processus continu. Il convient
que ce processus établisse le contexte externe et interne, apprécie les risques et les traite à l'aide d'un
plan de traitement des risques permettant de mettre en œuvre les recommandations et décisions.
La gestion des risques analyse les évènements susceptibles de se produire ainsi que leurs possibles
conséquences avant de décider de ce qui pourrait être fait, dans quels délais et à quel moment, pour
réduire les risques à un niveau acceptable.
Il convient que la gestion des risques en sécurité de l'information contribue à ce qui suit:
— l'identification des risques;
— l'appréciation des risques en termes de conséquences sur les activités métier et de vraisemblance;
— la communication et la compréhension de la vraisemblance et des conséquences de ces risques;
— l'établissement d'un ordre de priorité pour le traitement des risques;
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— la définition des priorités d'actions afin de réduire les occurrences des risques;
— l'implication des parties prenantes lors de la prise de décisions relatives à la gestion des risques et
l'information sur l'état de la gestion des risques;
— l'efficacité de la supervision du traitement des risques;
— la surveillance et le réexamen réguliers des risques et du processus de gestion des risques;
— la capture de l'information afin d'améliorer l'approche de gestion des risques;
— la formation des dirigeants et du personnel sur les risques et les actions à entreprendre pour les
atténuer.
Le processus de gestion des risques en sécurité de l'information peut s'appliquer à l'organisme dans son
ensemble, à toute partie distincte de l'organisme (à titre d'exemples un département, un lieu physique,
un service), à tout système d'information existant ou prévu, ou à des types particuliers de mesures de
sécurité (par exemple la planification de la continuité d'activité).
6 Présentation générale du processus de gestion des risques en sécurité de
l'information
Un aperçu de haut niveau du processus de gestion des risques est spécifié dans l’ISO 31000 et illustré à
la Figure 1.
Figure 1 — Processus de gestion des risques
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La Figure 2 illustre la manière dont le présent document applique ce processus de gestion des risques.
Le processus de gestion des risques en sécurité de l'information inclut l'établissement du contexte
(Article 7), l'appréciation des risques (Article 8), le traitement des risques (Article 9), l'acceptation des
risques (Article 10), la communication et la concertation relatives aux risques (Article 11), ainsi que la
surveillance et le réexamen des risques (Article 12).
Figure 2 — Illustration du processus de gestion des risques en sécurité de l'information
Comme l'illustre la Figure 2, le processus de gestion des risques en sécurité de l'information peut
être itératif pour les activités d'appréciation et/ou de traitement des risques. Une approche itérative
de conduite de l'appréciation des risques permet d'approfondir et de préciser l'appréciation à chaque
itération. Cette approche itérative assure un bon équilibre entre la minimisation du temps et des
efforts investis dans l'identification des mesures de sécurité et l'assurance que les risques élevés sont
correctement appréciés.
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Le contexte est établi en premier lieu. Une appréciation des risques est ensuite réalisée. Si cette
appréciation donne suffisamment d'informations pour déterminer correctement les actions nécessaires
pour ramener les risques à un niveau acceptable, la tâche est alors terminée et suivie par le traitement
des risques. Si les informations ne sont pas suffisantes, une autre itération de l'appréciation des risques
est réalisée avec un contexte révisé (par exemple les critères d'évaluation du risque, les critères
d'acceptation des risques ou les critères d'impact) et, éventuellement, sur des parties limitées de
l'ensemble du domaine d'application (voir la Figure 2, point de décision relatif au risque n° 1).
L'efficacité du traitement des risques dépend des résultats de l'appréciation des risques.
Il est à noter que le traitement des risques implique un processus cyclique de:
— appréciation d'un traitement des risques;
— décision de reconnaître si les niveaux de risque résiduel sont acceptables;
— génération d’un nouveau traitement des risques si les niveaux de risque ne sont pas acceptables; et
— appréciation de l’efficacité du traitement considéré.
Il est possible que le traitement des risques ne donne pas immédiatement un niveau acceptable de
risque résiduel. Dans ce cas, une nouvelle itération de l'appréciation des risques utilisant, si nécessaire,
de nouveaux paramètres de contexte (à titre d'exemples l'appréciation des risques, l'acceptation des
risques ou les critères d'impact) peut être requise et suivie d'un autre traitement des risques (voir la
Figure 2, Point de décision relatif au risque n° 2).
L'activité d'acceptation des risques doit garantir que les risques résiduels sont explicitement acceptés
par les dirigeants de l'organisme. Elle est particulièrement importante dans une situation où la mise en
œuvre de mesures de sécurité est omise ou reportée, par exemple en raison des coûts.
Au cours de l’ensemble du processus de gestion des risques en sécurité de l'information, il est important
que les risques et leur traitement soient communiqués aux dirigeants et au personnel concerné. Avant
même le traitement des risques, les informations relatives aux risques identifiés peuvent être très
utiles pour gérer les incidents et contribuer à réduire les dommages potentiels. La sensibilisation des
dirigeants et du personnel aux risques, la nature des mesures de sécurité mises en place pour atténuer
les risques et les problèmes rencontrés par l'organisme sont utiles pour gérer les incidents et les
événements imprévus de la manière la plus efficace. Il convient de documenter les résultats détaillés de
toute activité du processus de gestion des risques en sécurité de l'information, ainsi que ceux obtenus à
partir des deux points de décision de risque.
L'ISO/IEC 27001 spécifie que les mesures de sécurité mises en œuvre dans le domaine d'application, les
limites et le contexte du SMSI doivent être fondées sur le risque. L'application d'un processus de gestion
des risques en sécurité de l'information peut répondre à cette exigence. De nombreuses approches
permettent de déterminer les mesures de sécurité pour mettre en œuvre les options choisies en matière
de traitement des risques.
Il convient que l’organisme établisse, mette en œuvre et tienne à jour des procédures pour identifier les
exigences légales applicables pour:
— la sélection des critères pour l’évaluation des risques (7.2.2), l’impact des risques (7.2.3) et
l’acceptation des risques (7.2.4);
— la définition du domaine d'application et des limites de la gestion des risques en sécurité de
l'information (7.3 et A.2);
— l'évaluation des risques (8.4);
— le traitement des risques (9.1) et la mise en œuvre de plans de réduction des risques (9.2 et Annexe F);
— la surveillance, la revue et l’amélioration de la gestion des risques (12.2);
— l’identification des actifs (B.1.3) et la valorisation des actifs (B.2.3); et
© ISO/IEC 2018 – Tous droits réservés 5

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ISO/IEC 27005:2018(F)

— l’estimation des risques (voir les exemples en E.2.1).
7 Établissement du contexte
7.1 Considérations générales
Éléments d'entrée: Toutes les informations relatives à l'organisme permettant l'établissement du
contexte de la gestion des risques en sécurité de l'information.
Action: Il convient d'établir le contexte externe et interne de la gestion des risques en sécurité de
l'information, ce qui implique de déterminer les critères de base nécessaires à la gestion des risques
en sécurité de l'information (7.2), de définir le domaine d'application et ses limites (7.3) et d'établir une
organisation adaptée au fonctionnement de la gestion des risques en sécurité de l'information (7.4).
Préconisations de mise en œuvre:
Il est essentiel de déterminer l'objectif de la gestion des risques en sécurité de l'information puisqu'il
influence l'ensemble du processus et, en particulier, l'établissement du contexte. L'objectif peut être:
— une réponse aux exigences d'un SMSI;
— la conformité avec la loi et la preuve de la mise en œuvre du devoir de précaution;
— la préparation d'un plan de continuité d'activité;
— la préparation d'un plan de réponse aux incidents; et
— la description des exigences en matière de sécurité de l'information pour un produit, un service ou
un mécanisme.
Les préconisations de mise en œuvre des éléments d'établissement du contexte nécessaires pour
répondre aux exigences d'un SMSI sont traitées en 7.2, 7.3 et 7.4.
Éléments de sortie: La spécification des critères de base, le domaine d'application et ses limites,
et l'organisation dédiée au fonctionnement du processus de gestion des risques en sécurité de
l'information.
7.2 Critères de base
7.2.1 Approche de gestion des risques
Selon le domaine d'application et les objectifs de la gestion des risques, différentes approches peuvent
s'appliquer. L'approche peut également être différente pour chaque itération.
Il convient de choisir ou d'élaborer une approche de gestion des risques adaptée
...