Incident Analysis: Determining what actually happened

Auditors ask about incident analysis early, because the answer tells them how the rest of the program is likely to look. The outcome is NIST CSF 2.0 RS.AN-03.

What the framework says

NIST CSF 2.0 RS.AN-03 sets the expectation for incident analysis. The framework describes the outcome rather than prescribing a technology, so the question is whether your implementation achieves it and whether you can show that it does.

What this looks like in practice

On the ground, NIST CSF 2.0 RS.AN-03 is not one check. It resolves into several questions, and each one is really asking for different evidence:

• Does the organization apply the §164.402 breach standard correctly, treating any impermissible acquisition, access, use, or disclosure of PHI as PRESUMED to be a breach unless it documents a low probability that the PHI has been compromised, based on the four required factors, and does it recognize the three exceptions and the encryption safe harbor?
• Does the organization maintain a documented incident response plan defining what constitutes a security incident and covering detection, analysis, containment, eradication, and recovery?

Ownership usually sits with the security official, though the evidence is often produced by someone else, which is where the trail breaks. A control that works but has no owner tends to stop working the month the person who quietly maintained it changes roles.

Who this applies to

NIST CSF 2.0 is voluntary rather than binding, and that changes how it should be used. Adopting it does not create a legal obligation, and declining it is not a violation. It earns its place when a customer contract names it, when it gives structure to a program HIPAA describes only in outcomes, or when a recognized practice is worth having on record. Treat it as a way of organizing work you already owe, if HIPAA applies to you, not as a second regime.

Building it, in order

The sequence below is the order that produces evidence as a by-product rather than as a separate documentation exercise:

1. Adopt a written breach risk-assessment form that starts from the presumption rather than from a judgment call, and that requires a recorded finding on each of the four factors in 45 CFR 164.402 (the definition of breach, paragraph (2)) before any no-breach conclusion can be reached. Include a checklist for the three exceptions in 45 CFR 164.402 (the definition of breach, paragraph (1)), good-faith unintentional acquisition by a workforce member acting within scope, inadvertent disclosure between persons authorized at the same organization or organized health care arrangement, and a good-faith belief the recipient could not reasonably have retained the information, noting that the first two also require no further impermissible use or disclosure. Record the encryption status of the affected data, because encrypted PHI meeting the HHS guidance is not unsecured PHI and does not trigger notification. Retain every completed assessment for six years, including those concluding no breach occurred, since a no-breach determination you cannot evidence is indistinguishable from a breach you failed to report.
2. Maintain a written incident response plan that defines a security incident and documents each phase: preparation, detection and analysis, containment, eradication, recovery, and post-incident review.
3. Assign roles and responsibilities and include decision criteria for escalation.
4. Address scenarios with widespread impact, including mass-encryption events, with isolation and clean-restoration procedures.
5. Review and update the plan at least annually.

Where this meets HIPAA

Where encryption takes PHI outside the notification duties, it is because of how 45 CFR 164.402 defines unsecured protected health information: PHI "that is not rendered unusable, unreadable, or indecipherable to unauthorized persons through the use of a technology or methodology specified by the Secretary in the guidance issued under section 13402(h)(2) of Public Law 111-5."

For a healthcare organization the practical reason to care is the overlap with HIPAA. In our reading this outcome covers some of the same ground as 45 CFR 164.308(a)(6)(i) and 45 CFR 164.402. That is an editorial mapping, not an official NIST or HHS crosswalk, so read the HIPAA provision itself before relying on it; where the overlap holds, the evidence you produce can be cited against both so long as it is written once and kept in one place.

Evidence an assessor asks for

For this outcome the evidence types that satisfy it are plan and procedure. The distinction matters more than it looks: a policy states what you intend to do, a procedure states how, and a record proves it happened on a date. Auditors ask for all three, and a practice that has written the first two often has nothing for the third.

Date every document and keep the superseded versions. No federal rule sets a retention period for a voluntary framework document, so this is our recommendation rather than a requirement: keep six years, because that is what HIPAA requires of the documentation this work usually overlaps with (45 CFR 164.316(b)(2)(i) for security documentation, 164.530(j)(2) for privacy), and holding two sets of dates is how the earlier one goes missing.

Where this usually goes wrong

The usual cause of a gap here is drift: the control was implemented once, the environment changed, and nothing re-checked it. A dated review on a fixed cadence is cheaper than the remediation.

What to do about it

• Produce the evidence, not the intention. For NIST CSF 2.0 RS.AN-03 that means a written plan naming who does what, and evidence it was tested and a step-by-step procedure someone unfamiliar with the task could follow. If the only evidence is that someone knows how this works, you have a practice and not a record.
• Put a name on it. Your security official should be recorded as the owner. A control with no owner stops working the month the person who quietly maintained it changes roles, and nobody notices.
• Review it on a fixed date, not when you remember. Put the review on the calendar with an owner, and keep the dated output of each one.
• Keep the two sources apart. The framework outcome is voluntary. The steps above that cite 45 CFR are not: for a covered entity or business associate they are obligations in their own right.

Work backward from the evidence. Decide what evidence would prove incident analysis to someone who does not already trust you, then build the control that produces it. Programs built in that order tend to stay current, because the evidence goes stale visibly.

Related outcomes

• Incident Management Execution: Running an incident from detection to closure
• Internal and External Notification: HIPAA notification duties beside the CSF outcome
• Event Information Sharing: Getting event data to the people who act on it

References

• RS.AN-03, in NIST Cybersecurity Framework 2.0. This is a voluntary framework, not a legal requirement.
• The HIPAA provisions this post names are an editorial reading of where the work overlaps, not an official NIST or HHS crosswalk.
• This post describes what a framework outcome asks for and what evidence documents it. It is not legal advice, and your counsel owns the conclusion. State law may impose additional obligations of its own.