Thursday, 28 May 2009

Obstacle Poker for Security Assessments

I was talking to Vic Page, a colleague of mine, today about various things and he told me about one of his PhD deliverables on 'Three Card RAG' or 'Obstacle Poker' - very interesting concept that he has come up with. During our discussion, we came up with an embryonic idea for using his concept to aide security assessments of organisations. Before I can describe it I need to extract a few concepts from his 10-page paper in the BT Technology Journal entitled "Security risk mitigation for information systems".

In the paper he describes the Security Obstacle Mitigation Model (SOMM) for developing trustworthy information systems. He also defines some terminology - a subset of which I have reproduced here (his paper is an interesting read):

  • mitigation - a mitigation is a procedure that will counter the effect of an obstacle

  • obstacle - an obstacle is something that, should it occur, will obstruct a trust assumption and affect the CIAA security requirements - obstacles are caused by malicious or inadvertent use of the operational information system

  • RAG code - RAG codes form an intuitive 'traffic light' approach to ranking the ability for load-bearing and the vulnerability of a trust assumption (RAG is an acronym for Red, Amber and Green). R signifies stop and mitigate, A signifies proceed with caution and G signifies continue with trust

So how is this relevant to security assessments particularly rather than information systems in general? Well, it is the way he is applying it that becomes interesting for the security assessment arena. He has moved this concept into the field of agile development and taken the Scrums process of planning poker and made it more accessible for other fields.

Now a quick background to the security assessment field is in order. The majority of security assessment strategies are technology focused and concentrate on system evaluation and tactical issues. This can lead to point solutions and, therefore, gaps between countermeasures. Obviously we need the vulnerability assessments and information system audits, but these should follow an Information Security Risk Evaluation. Schemes like Octave, although big, do follow an organisational evaluation, focused on security practices and strategic issues. The top down approach is driven by business issues and objectives leading to protection of what needs it and awareness of risk. Most other bottom up security practices start with individual components and computing infrastructure, seeking the technological 'silver bullet', which leads to protecting what can be protected rather than what needs to be protected. Of course this is an ongoing cyclical process.


So, what is obstacle poker and how do we incorporate it into an information security risk evaluation? Well, the principle is that representatives of all roles must be included in an information security risk evaluation for it to meet the needs of the organisation. Too often security assessments are left to the ICT departments and technologists, who don't necessarily know the business processes at play. Unfortunately, the people working in the organisation who aren't part of the ICT team usually have little or no knowledge of the technical landscape or what's possible/feasible. It needs everyone at the table and they need to speak a common language. Interpreters, i.e. consultants, can be brought in to help, but there still needs to be a simple way to converse.

The idea of 'Three Card RAG' is that an issue is discussed and then all the members of the team will rate it with the RAG scale given above. This is done by issuing each member of the team three cards - one Red, one Amber and one Green. Each member picks a card and then everyone reveals their cards at once. If everyone agrees, then that is considered the state of play and actions are taken accordingly. If they do not agree then further discussion can be entered into and another round completed. The idea being to come to a consensus between the technical experts and the users of the system quickly and efficiently. Those that are more obvious will be dealt with very quickly, those requiring more discussion will be given a fair hearing.

This principle can be used in information security risk evaluation by identifying the threat ratings and consequences of risks. We all know that a Threat + a Vulnerability = Risk to an Asset, but how can we categorise these when ICT and management departments can be approaching this from very different standpoints? Is the system that seems critical to the ICT department actually critical to the business or not?

Threat ratings have the following defined ranges: Negligible, very low, low, medium, high, very high and extreme. They are quite well defined in terms of how often they are likely to occur, from unlikely, through likely to occur every 6 months or less for medium, to likely to occur multiple times each day for extreme. These threat ratings must be ICT lead, but not exclusively controlled. If everyone holds a green card then it can be classified as very low or negligible. Amber would denote Medium and red would denote very high or extreme threat rating. Mixtures of cards can result in the low or high ratings being used if there is still no total agreement after a few rounds. The consequences are where the ICT department may step back a little. These are defined by the Australian Government's Defence Signals Directorate as:

  • insignificant - can be dealt with by normal operations
  • minor - could threaten the system’s efficiency or effectiveness but can be dealt with internally
  • moderate - does not threaten the system, but could cause major review and modification of operating procedures
  • major - threatens the continuation of basic functions of the system and requires senior-level management intervention
  • catastrophic - threatens the continuation of the system and causes major problems for the organisation and customers

This is where Three Card RAG really comes into its own. Getting agreement on this scale can be very difficult in organisations. However, with a simple traffic light scheme, everyone understands the system and agreement can be reached much more easily between all the stakeholders. Simply put, if it's red it's a priority, amber is secondary and green can be safely ignored until the next iteration (N.B. not ignored completely or never discussed again, just not dealt with in the current round of the cycle).

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