Destined to be regularly enriched, those Questions & Answers (Q&A) deal with questions related to the implementation of the EBIOS method.
Answer from a Club EBIOS member: “We can act on several elements so that the result corresponds to the expectations”
Studies are sometimes criticized because of the combinatorial explosion of the elements to be studied. Therefore, before or at the beginning of any study, it is necessary to wonder what the sponsor is able to accept in terms of readability.Some wish to have as much detail as necessary to treat the risks (and/or justify the measures) in a fine way.
In this case, it is possible to handle the entire combination of events and threat scenarios.
If this is not the case, here are some tips that will help you reduce the entropy of the analysis:
Answer from a Club EBIOS member: “Two options”
Several proposals are possible to demonstrate that the problems associated with traceability are treated in an EBIOS study without considering traceability as a criterion:
Another answer’s response: “Traceability is not a security criterion”
The security criteria are used to assess the impacts in case of reaching each of them, and in particular to study the security needs. In information security, only availability, integrity and confidentiality are considered as security criteria (see in particular ISO/IEC 2700x).They should not be confused with the topics of security measures or regulatory references. Indeed, the (false) need for traceability comes from the fact that we want to know what happened after an incident (detection measure) and/or various obligations (legal, regulatory, sectoral or security policy-related). It is therefore useless and even counterproductive to study the need for traceability.
In addition, a scale of needs and a scale of impacts related to traceability should be available. It is often by trying to build them that one realizes that it is a “desire of someone” that falls under security measures or coverage of a legal “risk”.
Finally, this would involve studying all the threats that lead to the loss of traceability! Actually, this is related to the good implementation of a security measure, which is not necessary to treat as a risk (or otherwise it should be done for encryption, access control, etc.).
However, as the study of the needs is a communication tool with business, it is possible to integrate traceability into the security criteria so that business becomes more involved in the process by seeing its point of view taken into account…
Answer from a Club EBIOS member: “Pay attention to scales using several types of impacts”
EBIOS guide reminder: “This action [scale development] consists of creating a scale describing all possible levels of impacts, just like the scales of needs, a scale of impact levels is usually ordinal (the objects are classified in order of magnitude, the numbers indicate ranks and not quantities) and composed of several levels to classify all risks“.Therefore, it is usual to see users of the method build several ordinal scales depending on the nature of the impact (financial, legal, operations, privacy…) to estimate the severity of the feared events. The construction is then done by individually scaling each type of impact, without worrying about the consistency between the levels.
However, only a global result is used in risk maps to assess the severity of each compared to the others. Information on the nature of the impacts is lost.
To avoid misleading conclusions about the importance of risks, care must be taken to check the transverse coherence of the gradation of impacts in the scales. For example, checking that the estimatation of a level 3 impact on operations will be of the same value for the organization as the financial and legal impacts of the same level.
Where possible, the pivotal criterion (for consistency) may be the financial scale. If this is not the case (often the case), the side-by-side impacts should be presented and their importance assessed by those seeking consensus. In this case, the scales can have empty boxes (level having no equivalence for all types of impacts considered). This can be the case when one estimates the loss of human lives for example.
It is sometimes difficult for managers to establish these scales in a generic way. A good solution is then to ask the stakeholders to prioritize the feared events after identifying the impacts, and build the scales based on this estimate.
Answer from another member: “It is useful to have heterogeneous impact scales, it is an important means of communication with the business”
In addition, the ideal is in my opinion:
This makes it easy to carry out a study of both information security and privacy by presenting side-by-side the impacts to the organization and the impacts to the individuals (data subjects).