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ISO/IEC 27005
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ISO/IEC 27005:2011 Information technology — Security techniques — Information security risk management  (second edition)


The ISO27k standards are deliberately risk-aligned, meaning that organizations are encouraged to assess the security risks to their information (called “information security risks” in the standards, but in reality they are simply information risks) as a prelude to treating them in various ways. Dealing with the highest risks first makes sense from the practical implementation and management perspectives.

Scope of the standard

The standard ‘provides guidelines for information security risk management’ and ‘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.’

It cites ISO/IEC 27000 and the 2005 version of ISO/IEC 27001 as normative (essential) standards, and also mentions ISO/IEC 27002 in the scope section.

Content of the standard

At around 70 pages, ISO/IEC 27005 is a heavyweight standard although the main part is just 26 pages, the rest being mostly annexes with examples and further information for users.

The standard doesn't specify, recommend or even name any specific risk management method. It does however imply a continual process consisting of a structured sequence of activities, some of which are iterative:

  • Establish the risk management context (e.g. the scope, compliance obligations, approaches/methods to be used and relevant policies and criteria such as the organization’s risk tolerance or appetite);
  • Quantitatively or qualitatively assess (i.e. identify, analyze and evaluate) relevant information risks, taking into account the information assets, threats, existing controls and vulnerabilities to determine the likelihood of incidents or incident scenarios, and the predicted business consequences if they were to occur, to determine a ‘level of risk’;
  • Treat (i.e. modify [use information security controls], retain [accept], avoid and/or share [with third parties]) the risks appropriately, using those ‘levels of risk’ to prioritize them;
  • Keep stakeholders informed throughout the process; and
  • Monitor and review risks, risk treatments, obligations and criteria on an ongoing basis, identifying and responding appropriately to significant changes.

Extensive appendices provide additional information, primarily examples to demonstrate the recommended approach.

Status of the standard

The second edition of ISO/IEC 27005 was published in 2011. It reflects the general corporate or enterprise-wide risk management standard ISO 31000:2009 “Risk management - Principles and guidelines” in the specific context of risks to or involving information.

A project to revise the standard in line with the 2013 versions of ISO/IEC 27001 and 27002 made insufficient progress and was cancelled and re-started.  The project may develop a new standard “Guidance on managing  information security risks and opportunities” - a title referring to section 6.1 of ISO/IEC 27001:2013.  The project proposal is ambiguous re its relationship to ISO 31000 though.

December update An extensive technical corrigendum to the 2011 standard has been drafted and will be discussed at the next SC 27 meeting in April 2017 in Hamilton, New Zealand.

Further reading

Read more about selecting suitable information risk analysis methods and management tools in the ISO27k FAQ.

Personal comments

The committee has got itself in a pickle over the boilerplate wording imposed by JTC1 on ISO/IEC 27001. I believe the 27001 section 6.1 heading “Actions to address risks and opportunities” actually concerns risks to and opportunities for the management system, not information. Risk is evidently a trigger word for infosec pros. Many of them instantly assume risk refers to information security, but it is of course a much more general concept.  Doh!

A color-coded two-dimensional graphic remarkably similar to the one I described as an “Analog Risk Assessment” (ARA) metric was at one point proposed for inclusion in the standard, then reverted to a typical risk matrix with a mathematical calculation based on adding ordinal numbers assigned to levels of likelihood and consequence.  However, simple arithmetic is invalid for ordinals, making this approach technically invalid (although commonplace). Furthermore, cells in the body of the risk matrix are colored red for unacceptable or uncolored for acceptable, totally ignoring wide variations in each category. In fact I find the very concept of categorizing likelihoods, consequences, risks and acceptability unnecessary and unhelpful, compared to simply ranking them relative to each other on continuous scales.  Risks don’t fit into neat little boxes, and often extend over substantial ranges since both probabilities and impacts can only be estimated, and a given ‘risk’ may in fact consist of a family of related incidents.