Furthering the discussion on how detection in depth works, here is an example that folks have been asking me to demonstrate. This is a diagram that shows an asset, in this case PII in a database that is accessed via a PHP web application. The diagram shows the various controls around detection in place to protect the data at the various focus levels for detection. As explained in the maturity model post before, the closer the detection control is to the asset, the higher the signal to noise ratio it should be and the higher the relevance o the data should be to the asset being protected (Huston’s Postulate).
Hopefully, this diagram helps folks see a working example of how detection in depth can be done and why it is not only important, but increasingly needed if we are going to turn the tide on cyber-crime.
As always, thanks for reading and feel free to engage with ideas in comments or seek me out on Twitter (@lbhuston) and let me know what you think.
I have been discussing the idea of doing detection depth pretty heavily lately. One of the biggest questions I have been getting is about maturity of detection efforts and the effectiveness of various types of controls. Here is a quick diagram I have created to help discuss the various tools and where they fit into the framework of detection capability versus maturity/effectiveness.
The simple truth is this, the higher the signal to noise ratio a detection initiative has, the better the chance of catching the bad event. Detections layered together into various spots work better than single layer controls. In most cases, the closer you get to an asset, the more nuanced and focus (also higher signal to noise ratio) the detection mechanisms should become.
That is, for example – a tool like a script detecting new files with “base64decode()” in them on a web server is much higher signal than a generic IDS at the perimeter capturing packets and parsing them against heuristics.
When the close controls fire an alert, there better be a clear and present danger. When the distant controls alert, there is likely to be more and more noise as the controls gain distance from the asset. Technology, detection focus and configuration also matter A LOT.
All of that said, detection only works if you can actually DO something with the data. Alarms that fire and nothing happens are pretty much useless tools. Response is what makes detection in depth a worthwhile, and necessary, investment.