Still Using Excel for Risk Assessments?

Tuesday, July 27, 2010

Danny Lieberman

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There is a school of thought that says that you can take any complex problem and break it down like swiss cheese.

Risk assessment data collection and analysis with Excel is one of those problems that can’t be swiss-cheesed.  A collection of brittle, unwieldy, two dimensional worksheets is a really bad way of doing multi-dimensional modeling.

Consider that a typical risk assessment exercise will have a minimum of 4 dimensions (assets, threats, vulnerabilities and controls) and I think you will agree with me that Excel is a poor fit for risk assessment.

Here is where PTA (Practical Threat Analysis) comes to the rescue. You can download the free risk assessment software and try it yourself.

Any risk assessment process can be automated using Practical Threat Analysis and the PTA threat modeling database.  PTA is a threat modelling methodology and software tool that has been downloaded over 15,000 times and has thousands of active security analyst users on a daily basis.

PTA (Practical Threat Analysis) was first introduced in a paper by Ygor Goldberg titled “Practical Threat Analysis for the Software Industry” published online at Security Docs in October 2005. PTA provides a number of meaningful benefits for security and compliance risk assessments:

  • Quantitative: enables business decision makers to state asset values, risk profile and controls in familiar monetary values. This takes security decisions out of the realm of qualitative risk discussion and into the realm of business justification.
  • Robust: enables analysts to preserve data integrity of complex multi-dimensional risk models versus Excel spreadsheets that tend to be unwieldy, unstable and difficult to maintain.
  • Versatile: enables organizations to reuse existing threat libraries in new business situations and perform continuous risk assessment and what-if analysis on control scenarios without jeopardizing the integrity of the data.
  • Effective: recommends the most effective security countermeasures and their order of implementation. In our experience, PTA can help a firm mitigate 80% of the risk at 20% of the total control cost.

The PTA calculative model is implemented in a user-friendly Windows desktop application available as a freeware at the PTA Technologies web site. A PTA ISO 27001 library is available as a free download and is licensed under the Creative Commons Attribution License.

The need for cost effective risk reduction

Despite the importance of privacy and governance regulation, compliance is actually a minimum but not sufficient requirement for risk management.

The question is: What security controls should a firm implement after a risk assessment?

Taking ISO 27001 as a baseline security standard with a comprehensive set of controls, the ISO 27001 certification process can be as simple or as involved as an organization wants but there are always far more available controls than threats. As a result, organizations, large and small, find themselves coping with a long and confusing shopping list of controls. You can implement the entire checklist of controls (if you have deep pockets), you can do nothing or you can try and achieve the most effective purchase and risk control policy (i.e. get the most for your security investment dollar) with a set of controls optimized for your business situation.

However, implementing additional controls does not necessarily reduce risk.

For example, beefing up network security (like firewalls and proxies) and installing advanced application security products is never a free lunch and tends to increase the total system risk and cost of ownership as a result of the interaction between the elements and an inflation in the number of firewall and content filtering rules.

Firms often view data asset protection as an exercise in Access Control (Section 11 of ISO 27001) that requires better permissions and identity management (IDM). However, further examination of IDM systems reveals that (a) IDM does not mitigate the threat of a trusted insider with appropriate privileges and (b) the majority of IDM systems are notorious for requiring large amounts of customization (as much as 90% in a large enterprise network) and may actually contribute additional vulnerabilities instead of lowering overall system risk.

The result of providing inappropriate countermeasures to threats is that the cost of attacks and security ownership goes up, instead of risk exposure going down.

How to choose cost-effective controls

A PTA threat model enables a risk analyst to discuss risk in business terms with her client and construct an economically justified set of security controls that reduces risk in a specific customer business environment. A company can execute an implementation plan for security controls consistent with its budget instead of using an  all-or-nothing checklist designed by a committee of experts who all work for companies 100x the size of your operation.

Cross-posted from Israeli Software

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