ERNW Rapid Risk Assessment (RRA), Some Additional Notes, Part 1

At several occasions we’ve been asked to provide some background on the Rapid Risk Assessment (RRA) methodology we frequently use for a transparent (and documented) understanding of risks in certain situations and to deliver structured input for subsequent decision taking. As I had to write down (in another context) some notes on risk assessments and – from our perspective – practical, reasonable ways of performing them, I take the opportunity to lay out a bit the underlying ideas of the RRA approach. Which, btw, is no rocket science at all. Honestly, I sometimes wonder why stuff like this isn’t practiced everywhere, on a daily basis 😉

Here we go, second part to follow shortly. Feel free to get back to us with any comments, criticism, case studies, whatever. Thanks,



1. Introduction

There’s a number of heterogeneous definitions of the term “risk”, quite some of them with an inconsistent or ambiguous meaning and use[1]. In the following we will rely on the definitions furnished by the standard documents ISO 31000 Risk management — Principles and guidelines (providing a widely recognized paradigm for risk management practitioners from different backgrounds and industry sectors[2]) and ISO/IEC 27005 Information technology — Security techniques — Information security risk management (with a dedicated focus on the information security context).

ISO 31000 simply defines risk simply as

             “effect of uncertainty on objectives”

where uncertainty is “the state, even partial, of deficiency of information related to, under­standing or knowledge of an event, its consequence, or likelihood”[3] [ISO31000, p. 2].

Accepting uncertainty as being the main constituent of risk is a fundamental prerequisite for our approach outlined below. It must be well understood that first a certain degree of uncertainty is intrinsic to dealing with risks[4] and second that there’s always a trade-off bet­ween the – given resource constraints and human bounded rationality[5] – necessary reduction of complexity and (presumed) accuracy during an exercise of risk assessment.

[ISO31000, p. 8] emphasizes that “the success of risk management will depend on the ef­fectiveness of the […] framework” and [ISO31010[6], p. 18] concludes that “a simple method, well done, may provide better results than a more sophisticated procedure poorly done.”

Or, to express it “the blog way”: going with a simple method and thereby preserving the ability to perform exercises in a time-efficient manner, while accepting some fuzziness, will usually provide better results (e.g. for well-informed decision making) than striving for the big hit of a comprehensive risk enlightenment considering numerous potential dependencies and illuminating various dimensions of security objectives (which usually gets finished at the very moment Godot arrives).

2. Sources of Threats

In general two main possible approaches can be identified here:

  1. Use of a well-defined threat catalogue (usually one and the same at different points of execution) which might be provided by an industry association, a standards body or a government agency regulating a certain industry sector. While this may serve the common advantages of a standards based approach (accelerated setup of overall procedure, easy acceptance within peer community etc.), [ISO31010, p. 31] lists some major drawbacks of this course of action, laying out that check-lists    
    • tend to inhibit imagination in the identification of risks;
    • address the ‘known knowns’, not the ‘known unknowns’ or the ‘unknown unknown’.
    • encourage ‘tick the box’ type behavior
    • tend to be observation based, so miss problems that are not readily seen.


  • Adoption of (mostly) individual threats for individual risk assessment performances, depending on the amount of available resources, the context and “the question to be answered by means of the exercise”. This certainly requires more creativity and most notably experience on the participating contributors’ side, but will generally produce better and more holistic results in a more time-efficient way.

One essential element of the RRA is to (only + strictly) follow the latter approach (individual threats, depending on context). This means that some key players of the exercise-to-be-performed have to figure out the main threats before the proper risk assessment’s performance (usually by email) and that additional threats are not allowed later on. Again, in our perception, this is one of the critical success factors of the approach!

3. Contributing Factors

ISO 27005 (currently, that is as of 2008) defines information security risk as the

                    “potential that a given threat will exploit vulnerabilities of an asset […]
                     and thereby cause harm to the organization”.

Following this, three main factors contribute to the risk associated with a given threat:

  • the threat’s potential
  • the vulnerabilities to-be-exploited
  • the harm caused once the threat successfully materializes.

There’s a vast consensus amongst infosec risk assessment practitioners – and this is reflected by the way the wikipedia article on “risk” explains information security risk – that it hence makes sense to work with an explicit “vulnerability factor” expressing how vulnerable an asset is in case a threat shows up, for two main reasons:

  • When thinking about threats, this allows to differentiate between “external pheno­mena” (malware is around, hardware fails occasionally, humans make errors) and “internal conditions” (“our malware controls might be insufficient”, “we don’t have clustering of some important servers”, “our change control procedures are circumvented too often”).
  • This differentiation allows for governance and steering in the phase of risk treatment (“we can’t change [the badness of] the world, but we can mitigate our vulnerability”;  which then is expressed by a diminished vulnerability factor and subsequently reduced overall risk.)

This furthermore facilitates looking at some asset’s (e.g. a product’s) intrinsic pro­perties (leading to vulnerabilities) without knowing too many details about the environment the asset is operated in.

[1] The wikipedia article on the subject might serve as a starting point.

[2] Based on AS/NZS 4360 which in turn is regarded as a major contribution to the mainstream concept of risk in the 20th century.
The definition of the term “risk” within ISO 31000 is taken from ISO GUIDE 73:2009 and it can be expected that future versions of ISO 27005 will incorporate this definition (and the underlying idea) as well.

[3] It should be noted that the terms (and concepts) of “risk” and “uncertainty” might dispose of some duality on their own (see [COFTA07, p. 54ff.] for a detailed discussion on this). Still, we strictly follow the ISO 73 approach here.

[4] Where “assessing them” is one step in “dealing with risks”.

[5] [COFTA07, p.29] employs the concept of a “transactional horizon” to express the inherent limitations. Furthermore see [KAHNEMANN] or [SIMON] on bounded rationality.

[6] ISO 31010 gives an overview of risk assessment techniques.

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