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 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 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.
A project to revise the standard is in progress, re-aligning ISO/IEC 27003, 27004 and 27005 with the 2013 versions of ISO/IEC 27001 and 27002, and the current release of ISO 31000 concerning enterprise risk management.
Nearly 100 pages of comments have been received on the Working Draft. Several are concerned with improving the alignment with ISO 31000 and Guide 73, for instance “impact” may be dropped in favour of “consequence” - though perhaps not!
Read more about selecting suitable information security risk analysis methods and tools in the ISO27k FAQ.
A graphic remarkably similar to the one I described as an “Analog Risk Assessment” (ARA) metric has been proposed for the standard, along with a general move to describe and compare risks in terms of the combination of probability of their occurrence and the business consequences if they were to occur. I am still developing useful new applications for the ARA approach, and plan to write a paper on it as soon as I have the time.