Control statement
Reimplement or custom develop the following critical system components: [Organization-defined: critical system].
Discussion
Organizations determine that certain system components likely cannot be trusted due to specific threats to and vulnerabilities in those components for which there are no viable security controls to adequately mitigate risk. Reimplementation or custom development of such components may satisfy requirements for higher assurance and is carried out by initiating changes to system components (including hardware, software, and firmware) such that the standard attacks by adversaries are less likely to succeed. In situations where no alternative sourcing is available and organizations choose not to reimplement or custom develop critical system components, additional controls can be employed. Controls include enhanced auditing, restrictions on source code and system utility access, and protection from deletion of system and application files.
Organization-defined parameters
These values must be resolved through the organization’s tailoring and governance process. Bracketed parameter references in the control text identify where a decision is required.
From control text to operational evidence
Use Customized Development of Critical Components as a testable risk decision. Translate the official statement into accountable people, repeatable processes, configured technology, and evidence that demonstrates the outcome over time. In this family, pay particular attention to secure acquisition, engineering, development lifecycle, supplier expectations, and system integrity by design.
Implementation workflow
- Define the control boundary, responsible owner, inherited portions, and systems or processes in scope.
- Resolve each organization-defined parameter before declaring the control implemented.
- Document how the implementation satisfies every clause of the official control statement.
- Collect evidence as a normal byproduct of operation rather than only before an assessment.
- Review exceptions, changes, and monitoring results on a risk-based cadence.
Evidence examples
- security requirements in contracts and specifications
- architecture and design review records
- development lifecycle evidence
- supplier assessment and acceptance records
Common failure patterns
- security requirements added after procurement
- supplier claims accepted without evidence
- development exceptions become permanent
- security architecture not tied to testable requirements
Questions practitioners should ask
- What risk decision is this control intended to support in this system?
- Which parts are implemented locally, inherited, shared, or not applicable—and what evidence supports that decision?
- Do the documented narrative, deployed configuration, operating process, and collected evidence agree?
- What event or threshold requires the implementation to be reviewed or changed?
Assessment objectives and methods
Show the assessment objective
[Organization-defined: critical system] are reimplemented or custom-developed.
Examine
- Supply chain risk management plan
- system and services acquisition policy
- procedures addressing the customized development of critical system components
- system design documentation
- system configuration settings and associated documentation
- system development life cycle documentation addressing the custom development of critical system components
- configuration management records
- system audit records
- system security plan
- other relevant documents or records
Interview
- Organizational personnel with system and service acquisition responsibilities
- organizational personnel with information security responsibilities
- organizational personnel with responsibility for the reimplementation or customized development of critical system components
Test
- Organizational processes for the reimplementation or customized development of critical system components
- mechanisms supporting and/or implementing the reimplementation or customized development of critical system components
Related controls
These relationships come from the official OSCAL catalog. They indicate useful dependencies or context, not automatic inheritance or equivalence.
Authoritative sources
Bare Metal Cyber is an independent educational publisher and is not affiliated with or endorsed by NIST. Official control requirements and interpretations remain with NIST and the responsible authorizing organization.