NIST Revised their guidance on Incident Impact Assessment in The Computer Security Incident Handling Guide, SP 800-61 Revision 2, August 2012.

Revision 1 provided a complex measure for incident impact assessment that might provide insight in hindsight, but one that was not practical, applicable, or useful in the midst of an incident response. The new measures, suggested in the table above, are really quite useful, applicable, and discernible. There are 3 important impact areas with associated metrics:

  • Functional impact
  • Information Impact
  • Recoverability Effort

Functional Impact

This measures loss of system functionality. NONE – No loss of functionality. LOW – no loss of functionality, but loss of efficiency. MEDIUM – Critical services lost to a subset of users. HIGH –  Critical services lost to all users.

Information Impact

Here NIST stops short of measuring impact – so the above diagram is not colored for this Impact Area except in the case of NONE – no information was exfiltrated, modified, or deleted. An impact measure is needed for each of the three information impact areas. PRIVACY BREACH – personally identifiable information was compromised. PROPRIETARY BREACH – unclassified proprietary data was compromised. INTEGRITY LOSS – sensitive or proprietary information was changed or deleted. A level of impact measure is needed in each of these areas. The loss of a single document or individual’s data is low, but what defines medium or high?

Recover-ability Effort

This is an interesting and useful metric: Is the data/system recoverable? If so, what is the level of recovery effort? NOT RECOVERABLE – the data or system cannot be recovered. REGULAR – time-to-recover is predicable with existing resources. SUPPLEMENTED – time-to-recover is predictable, but with additional resources. EXTENDED – time-to-recover is unpredictable and additional resources including outside help are needed.

Coordinated Response

This new approach agrees with the Coordinated Response Impact Assessment in the Response Management Framework. The table below shows the 5 possible impact areas with associated impact metrics.

 NIST Impact Areas

Coordinated Response can help you review and improve your Incident Response Plan.

Leave A Comment

You must be logged in to post a comment.