# NIST SP 800-53 Rev. 5 SC-31 — Covert Channel Analysis

- Source: https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-31-covert-channel-analysis
- Section: [Compliance](https://support.icompaas.com/compliance) › [NIST SP 800-53 Rev. 5 Controls](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5) › SC — System and Communications Protection
- Last updated: 2026-06-05
- Publisher: iCompaas, Inc. (https://www.icompaas.com)

**NIST SP 800-53 Rev. 5**·Control `SC-31`·high·Component: **System and Communications Protection**

## What this control requires

> Perform a covert channel analysis to identify potential avenues for covert storage or timing channels within the system. Estimate the maximum bandwidth of these channels. Covert channel analysis is crucial when systems handle sensitive data, such as export-controlled information, or in multi-level secure systems, cross-domain systems, or systems with external network connections. This control supports the Covert Channel Detection System capability within the System and Communications Protection family.
> 
> — NIST SP 800-53 Rev. 5, Control SC-31

### In plain English

Perform a covert channel analysis to identify potential avenues for covert storage or timing channels within the system. In practice, this means you can prove you information management-level controls on a defined cadence.

## Why it matters

SP 800-53 is the catalogue every U.S. federal authorisation (FedRAMP, FISMA, CMMC) and most regulated industries point at. A missing control surfaces as a Plan of Action & Milestones (POA&M) item that an Authorizing Official must approve before the Authority To Operate is granted or renewed.

This control is rated **high**. Auditors expect a named owner, a remediation SLA, and a tooling artefact that evidences continuous operation.

## What an auditor looks for

A 3PAO (FedRAMP) or Independent Assessor (NIST RMF) tests against NIST SP 800-53A assessment procedures. For each control they expect a documented implementation that addresses every assessment objective (Examine, Interview, Test) and an implementation summary in the System Security Plan.

Within **System and Communications Protection**, the assessor will trace your implementation back to the catalogue reference (Control SC-31) and look for objective evidence on the latest two assessment cycles.

## How to implement

#### Cloud Posture

**CSPM.** Run Wiz / Prisma / Defender for Cloud / Security Command Center over every account; auto-ticket findings above your accepted-risk threshold.

#### Network Security

**AWS.** VPC Flow Logs to S3, default-deny security groups, AWS Network Firewall for north-south, and Transit Gateway for hub-and-spoke segmentation.

**Azure.** NSGs with deny-by-default, Azure Firewall Premium with TLS inspection, Private Endpoints for PaaS, and Microsoft Defender for Cloud's secure score for drift.

**GCP.** VPC Service Controls perimeters around sensitive APIs, Cloud NGFW Enterprise for L7 inspection, Private Service Connect for managed services.

#### Configuration Management

**Policy-as-code.** Codify the control as Service Control Policies (AWS), Azure Policy initiatives, or Organisation Policy (GCP) so the platform enforces what the document promises.

**IaC.** Gate Terraform / Pulumi / CloudFormation changes with Checkov / tfsec / OPA so misconfigurations never reach production.

**Drift.** Run a CSPM (Wiz / Prisma / Defender for Cloud / Security Command Center) over every account and route findings to a single risk register.

### Operational checklist

-   **Information.** Document the trigger, the owner and the cadence.
-   **Security.** Document the trigger, the owner and the cadence.
-   **Configuration.** Document the trigger, the owner and the cadence.
-   **Data.** Document the trigger, the owner and the cadence.
-   **Detection.** Document the trigger, the owner and the cadence.
-   **Scope:** management, information, system, analysis, protection, configuration, capability, storage.

## Evidence to collect

-   **Infra Scan.** Continuous infrastructure-posture telemetry — AWS Config, Azure Policy compliance, GCP Organisation Policy, Wiz / Prisma findings.

Infrastructure posture tooling (AWS Config, Azure Policy, Nessus) verifies platform hardening. Focus: Covert Channel Analysis.

## Common pitfalls

-   Treating CSPM findings as a backlog instead of a hot queue: findings older than the policy SLA accumulate until the auditor asks why.
-   Default-allow egress rules; East-West traffic with no segmentation; jump hosts on the public internet with password auth.
-   Manual cloud-console changes that never make it back to Terraform — drift accumulates until the next outage forces a reconciliation.

## How it maps to other frameworks

Computed from shared tags, control component and key-operation subjects — handy when you are reconciling controls across an audit.

-   [**NIST SP 800-171 Rev. 3 3.14.6** — System Monitoring](https://support.icompaas.com/compliance/nist-sp-800-171-rev-3/3-14-6-system-monitoring)

## Related controls in NIST SP 800-53 Rev. 5

-   [**Control SC-28(2)** — Offline Storage](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-28-2-offline-storage)
-   [**Control SC-7(5)** — Deny By Default -- Allow By Exception](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-7-5-deny-by-default-allow-by-exception)
-   [**Control SC-7(22)** — Separate Subnets For Connecting To Different Security Domains](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-7-22-separate-subnets-for-connecting-to-different-security-domains)
-   [**Control CP-9(3)** — Separate Storage For Critical Information](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/cp-9-3-separate-storage-for-critical-information)
-   [**Control SC-7(18)** — Fail Secure](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-7-18-fail-secure)
-   [**Control SC-25** — Thin Nodes](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-25-thin-nodes)

## References

-   [NIST Computer Security Resource Center — NIST SP 800-53 Rev. 5](https://csrc.nist.gov/Projects/risk-management/sp800-53-controls)
-   Catalogue identifier: `Control SC-31`

Topics: network securitydata protectioncloud postureconfiguration management

## Related compliance guidance

- [NIST SP 800-53 Rev. 5: a practical implementation guide for cloud teams](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5): Start with the full NIST SP 800-53 implementation guide — scope, roadmap, evidence and how the assessment runs.
- [NIST SP 800-171 and CMMC: a practical guide to protecting CUI in the cloud](https://support.icompaas.com/compliance/nist-sp-800-171-rev-3): If your obligation is protecting CUI in your own systems for a federal or defence contract, this derived subset — not the full catalogue — is the requirement.
- [SOC 2 compliance: a practical implementation guide for cloud-native SaaS teams](https://support.icompaas.com/compliance/soc-2-trust-services-criteria): Most commercial SaaS already hold a SOC 2 Type 2, and FedRAMP 20x Class A is designed for providers that have one.