NIST 800-53 assessments, from control gaps to ATO.

1. 01

   Categorisation and baseline selection

   System categorisation under FIPS 199 determines your control baseline — low, moderate or high. Getting this wrong at the start means assessing against the wrong control set, so it is worth the time up front.

2. 02

   Control assessment

   Each applicable control is assessed as implemented, partially implemented, planned or not applicable, with the rationale recorded. Not-applicable determinations need justification an assessor will accept, and that is where packages most often come back.

3. 03

   Evidence and testing

   Controls are tested rather than taken on assertion: examine the artefact, interview the operator, observe the mechanism. That is the assessment method the standard expects.

4. 04

   POA&M development

   Findings become a Plan of Action and Milestones with owners, resources and realistic dates. A POA&M with dates nobody can meet is worse than one with honest ones.

5. 05

   Documentation package

   System Security Plan, assessment report and POA&M assembled into the package an authorising official expects, written to be reviewed rather than to be voluminous.

6. 06

   Ongoing monitoring

   Authorisation is not the end. We advise on the continuous monitoring cadence that keeps the authorisation valid and stops the next assessment from starting over.

Common questions

What is NIST 800-53?

NIST 800-53 is the catalog of security and privacy controls that federal information systems must implement to protect government data. It is the backbone of FISMA compliance and the NIST Risk Management Framework (RMF), organized into control families, each with a low, moderate, or high baseline matched to a system's impact level. A NIST 800-53 assessment is central to obtaining an Authority to Operate (ATO).

How is NIST 800-53 related to FISMA and the RMF?

FISMA requires federal agencies and contractors to secure their information systems, and NIST 800-53 provides the control catalog they implement to do it. The NIST Risk Management Framework (RMF) is the process for selecting, implementing, assessing, and authorizing those controls. A NIST 800-53 assessment provides the control evidence the RMF and FISMA require, and that an ATO decision depends on.

What is an ATO and how does an assessment help?

An Authority to Operate (ATO) is the formal authorization for a federal system to run in production, granted after an authorizing official reviews its security posture. A NIST 800-53 assessment produces the control implementation evidence, risk assessment, and Plan of Action and Milestones (POA&M) that the ATO package requires, so you can reach and maintain authorization.

Which NIST 800-53 baseline applies to us?

It follows from your system categorisation under FIPS 199 — low, moderate or high, based on the impact of a confidentiality, integrity or availability failure. Getting the categorisation wrong means assessing against the wrong control set entirely, so it is worth the time at the start.

What is a POA&M and what makes a good one?

A Plan of Action and Milestones records findings with owners, resources and dates. A good one has dates the organisation can actually meet. A POA&M full of optimistic dates that slip is worse than one with honest ones, because it costs credibility with the authorising official you will need again.

Is NIST 800-53 the same as NIST 800-171 or CMMC?

Related but not the same. 800-171 addresses controlled unclassified information in non-federal systems and draws on 800-53; CMMC builds an assessment and certification model largely on 800-171. Which applies depends on your contracts, and we confirm that before scoping rather than assuming.

Do you support us after authorisation?

Yes. An ATO is not the finish line — it depends on continuous monitoring to stay valid. We advise on the cadence and evidence that keeps it current, so the next assessment builds on this one instead of starting over.