ISO/IEC 27005 Information technology -- Security techniques -- Information security risk management

This standard was published in June 2008.

“ISO/IEC 27005:2008 provides guidelines for information security risk management. It 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 ISO/IEC 27005:2008. ISO/IEC 27005:2008 is applicable to all types of organizations (e.g. commercial enterprises, government agencies, non-profit organizations) which intend to manage risks that could compromise the organization's information security.”

ISO/IEC 27005 revises the Management of Information and Communications Technology Security (MICTS) standards ISO/IEC TR 13335-3:1998 plus ISO/IEC TR 13335-4:2000.
Some personal comments on ’27005

[These are just my personal perspective. They inevitably reflect my own prejudices and limited experience with information security risk management.]

At around 60 sides, ISO/IEC 27005 is a heavyweight standard although the main part is just 24 pages, the rest being mostly annexes with examples and further information for users. There is quite a lot of meat on the bones, reflecting the complexities in this area.

Although the standard defines risk as “a combination of the consequences that would follow from the occurrence of an unwanted event and the likelihood of the occurrence of the event”, the risk analysis process outlined in the standard indicates the need to identify information assets at risk, the potential threats or threat sources, the potential vulnerabilities and the potential consequences (impacts) if risks materialize. Examples of threats, vulnerabilities and impacts are tabulated in the annexes; although incomplete, these may prove useful for brainstorming risks relating to information assets under evaluation. It is clearly implied that automated system security vulnerability assessment tools are insufficient for risk analysis without taking into account other vulnerabilities plus the threats and impacts.

The standard includes a section and annex on defining the scope and boundaries of information security risk management which should, I guess, be no less than the scope of the ISMS.

The standard deliberately remains agnostic about quantitative and qualitative risk assessment methods, essentially recommending that users choose whatever methods suit them best, and noting that they are both methods of estimating, not defining, risks. Note the plural - 'methods' - the implication being that different methods might be used for, say, a high-level risk assessment followed by more in-depth risk analysis on the high risk areas. The pros and cons of quantitative vs qualitative methods do get a mention.

The steps in the process are (mostly) defined to the level of inputs -> actions -> outputs, with additional “implementation guidance” in similar style to ISO/IEC 27002.

The standard incorporates some iterative elements e.g. if the results of an assessment are unsatisfactory, you loop-back to the inputs and have another run through. For those of us who think in pictures, there are useful figures giving an overview of the whole process and more detail on the risk assessment -> risk treatment -> residual risk bit.

From:iso27001security.com