Security Scenario Development

  • 17 March, 2017
  • Amsterdam Security
By Mr.drs. Jos de Lange EMFC, security coordinator at DSyS (TU Delft Safety and Security Institute), Delft, the Netherlands

Security professionals looking at security problems are often inclined to focus on security control measures. Commonly used techniques are putting up cameras and the use of zoning by applying tourniquets and the introduction of access control measures. Before security measures are taken, however, it is prudent to look at the broader context of the local security situation. The causes of local insecurity may lie much further away than is obvious at first sight. An example to clarify what we mean is the threat of terrorist attack. Where for some, the cause can be found in local conditions such as lack of education and opportunities for self-development, the causes according to other observers go deeper, like aggressive beliefs and the related subversion by Middle East states.

The only way for security professionals to avoid the political controversy that underlies these two assumptions is by making alternative threat scenarios that take account of different causes and different effects on the local threat perspectives.

Security threat scenario

According to the Nuclear Security & Safeguards Education Portal (NSSEP) a scenario is a detailed path that imagines a specific, realistic adversary attempt along a pathway. A security threat scenario includes additional information such as tasks, defeat techniques, equipment, possible collaboration with an insider and more. It can also include indirect attacks on physical protection system (PPS) components. Within a short period many threat scenarios can be devised for a single attack path. NSSE also draws attention to the threat of insider collusion, which may relate to insider tampering with alarm communication to thwart detection or adequate reaction of a response force. NSSE gives the following example of a scenario for a sabotage pathway.

Risk calculating

Scenario development has everything to do with risk and probability. An important element of imagining a realistic adversary attempt along a pathway is calculating the chance of that particular situation occur¬ring over a certain period of time. This is called calculating (security) probability. Security risk is running the probability that, given a certain set of circumstances, a certain threatening situa¬tion will occur with negative consequences. The aim of this risk calculating exercise is to design and implement effective intrusion barriers and response measures. The calculation of this event actually occurring over a certain amount of time, with given consequences, is called risk (Ale, 2009, p.5). (Ale, 2009, p. 5)

Bowtie: risk barrier diagram

A more elaborate approach to scenario building is that of using ‘Bow Tie’ or bowtie modeling for calculating various intrusion pathways. The conse¬quences of a deliberate attack on a critical asset such as a chemical plant could be wide ranging and depend on a number of variables, including: type of facility, failure or disruption mode, critical functions (water supply, hydroelectric power generation, navigation, etc.), system redundancies, down¬stream population density, regional infrastructure, and seasonal conditions (DHS, 2012). These cascading risks originate most times from a single occurrence, in this case the (part) failure of the security defense barrier(s) surrounding the plant. That occurrence however is preceded by other events leading to the dis-functioning, or even collapse, of the preventive security measures. This combination of (failure) causes and effects can be presented in a risk barrier diagram, as presented in the following figure. The bowtie combines risks, threats, preventive and remedial measures together in one model.

The Delft Safety & Security Institute (DSyS) has comprehensive and in-depth experience in the field of statistical analysis and the interpretation of the results for application in security practices. For more information contact Jos de Lange, DSyS security coordinator (

PPS : John J. Fay, Encyclopedia of Security Management, Butterworth-Heinemann/Elsevier, 2007

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