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SA-8(2) SA · System and Services Acquisition

Least Common Mechanism

LOW MODERATE HIGH
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Requirements NIST SOURCE

Implement the security design principle of least common mechanism in [systems or system components].

Discussion (NIST Supplemental Guidance)

The principle of least common mechanism states that the amount of mechanism common to more than one user and depended on by all users is minimized POPEK74 . Mechanism minimization implies that different components of a system refrain from using the same mechanism to access a system resource. Every shared mechanism (especially a mechanism involving shared variables) represents a potential information path between users and is designed with care to ensure that it does not unintentionally compromise security SALTZER75 . Implementing the principle of least common mechanism helps to reduce the adverse consequences of sharing the system state among different programs. A single program that corrupts a shared state (including shared variables) has the potential to corrupt other programs that are dependent on the state. The principle of least common mechanism also supports the principle of simplicity of design and addresses the issue of covert storage channels LAMPSON73.

Implementation Guidance

Engineering Interpretation

Original engineering commentary written for this explorer — not NIST source text and not authoritative guidance.

No engineering interpretation has been authored for SA-8(2) yet. This section is architected to receive it — see the Requirements and Assessment sections above for the authoritative NIST source content in the meantime.

Assessment

NIST SP 800-53A REV 5.2.0

Assessment Objectives

  1. systems or system components that implement the security design principle of least common mechanism are defined;
  2. <SA-08(02)_ODP systems or system components> implement the security design principle of least common mechanism.

Examine

[SELECT FROM: System and services acquisition policy; procedures addressing the security design principle of least common mechanism used in the specification, design, development, implementation, and modification of the system; system design documentation; security and privacy requirements and specifications for the system; system security and privacy architecture; system security plan; other relevant documents or records].

Interview

[SELECT FROM: Organizational personnel with the responsibility for determining system security and privacy requirements; organizational personnel with system specification, design, development, implementation, and modification responsibilities; system developers; organizational personnel with information security responsibilities].

Test

[SELECT FROM: Organizational processes for applying the security design principle of least common mechanism in system specification, design, development, implementation, and modification; mechanisms supporting the application of the security design principle of least common mechanism in system specification, design, development, implementation, and modification].

Overlays

Showing the OT/ICS overlay for the parent control SA-8 — see the SA-8(2) entries within each baseline below.

OT/ICS Overlay SP 800-82r3

NIST SP 800-82r3 Appendix F, Table 22. Blank baseline means the control/control enhancement is not selected in that initial OT baseline.

LOW

  • Base control: Included (matches standard baseline)

MODERATE

  • Base control: Included (matches standard baseline)

HIGH

  • Base control: Included (matches standard baseline)

STIGs & CCIs

No STIG checks or CCI mappings are currently loaded for SA-8(2). This section is architected to display, per product: STIG ID, Finding ID, Severity, Title, Description, Check, Fix, CCI, and NIST control mapping — but nothing is populated here until a real DISA STIG/CCI dataset is ingested.

Learn more about STIG/CCI integration →

Evidence

Potential Evidence — Derived

Categorized from the SP 800-53A "Examine"/"Test" artifact list above by keyword — not an authoritative NIST evidence list.

Policy

  • System and services acquisition policy
  • system security plan

Configuration

  • system design documentation
  • system security and privacy architecture

Testing

  • Organizational processes for applying the security design principle of least common mechanism in system specification, design, development, implementation, and modification
  • mechanisms supporting the application of the security design principle of least common mechanism in system specification, design, development, implementation, and modification

Other Records

  • procedures addressing the security design principle of least common mechanism used in the specification, design, development, implementation, and modification of the system
  • security and privacy requirements and specifications for the system
  • other relevant documents or records