Evaluating Operational Feasibility

I’ve discussed the concept of evaluating the operational “feasibility” (or “impact”, depending on your point of view) of security controls before. Some people approached me asking “which considerations should we take into account when trying to understand or rate this for $SOME_SECURITY_CONTROL?”. Therefore, in the following I’ll give an unordered list of factors to consider to get an understanding of the “operational feasibility” of a given security control. Two things should be noted in advance:

– evaluating the operational “feasibility” (which is “a positive factor”) as opposed to the operational “impact” (being a “negative factor”) allows for easier integration into a metric scheme, as the two main factors-to-considered – the other one is the “security benefit” of a control – can be expressed on the same scale then, with a high value meaning a good thing.
– as the (maturity of) and as-is state of operational processes usually have a much higher impact on the security posture of a given environment than the components deployed in the environment (see this presentation, slide 14ff.), this approach focuses on _operational costs_ and does not take initial investment costs into account. In short: opex is the thing to look at, not capex.
Here we go… for each (potential) security control you might look at:

a) How many lines of code/configuration does it need?

b) Can it be implemented by means of templates or scripts? Effort needed for this?

c) To what degree does the implementation differ in different scenarios (e.g. per system/subnet/site)? Can “the difference” be scripted, e.g. taken from another source (a CMDB) or “calculated” (like the addresses of neighboring routers on the local link)?

d) How much additional configuration is needed to establish the previous functionality/state? E.g. to pass legitimate traffic in case of a (“fresh”) application of ACLs?

e) What’s the “business impact” incl. number of associated support/helpdesk calls?

f) Cost for _deployment_ of additional hardware, licenses or other tangibles. (again, the cost for their initial procurement is capex).

g) In case of a tangible security control think about the full life-cycle management of the asset (patching, monitoring, alerting, capacity management and the like). This one is often heavily overlooked, see for example this excellent blog post of Anton Chuvakin for a discussion of the “real costs of a SIEM deployment”.

h) Does the control require a new operational process or task?

i) Propagation: how far does the (implementation of the) control reach?

j) How many different people or companies/partners (sub contractors) touch the work?

k) Impact on OLAs and SLAs.

The above might give an idea of how to tackle the task of evaluating the operational feasibility. In another, future blogpost I may discuss a sample metric using this stuff from a real-world environment (will have to write down and anonymize some pieces though). For the moment many thanks to Friedwart, Angus and Sergey for valuable input to the above list.

Feel free to contact us (or leave a comment) with suggestions as for additional considerations.

have a good one,


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