The InfoSec Blog

What is the goal behind calculating assets in ISO-27000?

Posted by Anton Aylward

My friend and colleague Gary Hinson said about asset valuation in ISO-27000

So, for instance, it’s hard to say exactly how much the HR database
is worth, but it’s a fair bet that it is less valuable to the
organization than the Sales and Marketing database containing
commercial details on customers and prospects. Therefore, it
probably makes commercial sense to put more effort and resources into
securing the S&M database against disclosure incidents, than for the
HR database.

While Gary is 'classically' right, there's a hidden gotcha in all that.

It is *YOU* that are assigning value, it is the value to YOU.
As Donn Parker points out, this may be quite different from the the value system of the attackers. You don't know their values, motivations, tools etc etc etc.

Risk Models that hide important information

Posted by Anton Aylward

Some people seem to be making life difficult for themselves with risk models such as "Impact * Probability" and as such have lead themselves into all manner of imponderable ... since this model hides essential details.

I discuss the CLASSICAL risk equation in my blog
http://infosecblog.antonaylward.com/2010/05/19/the-classical-risk-equation/

There is a good reason for, no make that MANY good reasons, for separating out the threat and the vulnerability and asset rather that just using "impact".

Any asset is going to be affected by many

  • threats
  • vulnerabilities
  • controls

Any control will almost certainly address many assets and in all likelihood deal with many threats and vulnerabilities.

Any reasonable approach will try to optimise this: make the controls more effective and efficient by having them cover as many assets, threats or vulnerabilities as possible.

As such, the CLASSICAL risk equation can then be viewed as addressing residual risk - the probability AFTER applying the controls.