NIST SP 800-53 Rev. 5 CP-11 — Alternate Communications Protocols

What this control requires

Employ alternative communications protocols to maintain continuity, integrating into contingency plans and testing for resilience, assessing impacts. This control supports the Network Protocol Switch capability within the Contingency Planning family.

In plain English

Employ alternative communications protocols to maintain continuity, integrating into contingency plans and testing for resilience, assessing impacts. In practice, this means you can prove you security 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.

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 Contingency Planning, the assessor will trace your implementation back to the catalogue reference (Control CP-11) 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.

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.

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.

Operational checklist

• Security. Document the trigger, the owner and the cadence.
• Configuration. Document the trigger, the owner and the cadence.
• Network. Document the trigger, the owner and the cadence.
• Control. Document the trigger, the owner and the cadence.
• Testing,. Document the trigger, the owner and the cadence.
• Scope: management, configuration, capability, communications protocols, security, configuration management.

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: Alternate Communications Protocols.

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.
• Manual cloud-console changes that never make it back to Terraform — drift accumulates until the next outage forces a reconciliation.
• Default-allow egress rules; East-West traffic with no segmentation; jump hosts on the public internet with password auth.
• DR plans that have never been tested in earnest, or that depend on an MFA token only one person can produce.

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 3.13.6 — Network Communications - Deny by Default - Allow by Exception
• ISO/IEC 27001:2022 A.8.22 — Segregation of networks
• BSI C5:2020 COS-04 — Cross-network access
• CIS Controls v8 13.4 — Perform Traffic Filtering Between Network Segments

Related controls in NIST SP 800-53 Rev. 5

• Control CP-6(2) — Recovery Time And Recovery Point Objectives
• Control CP-6(1) — Separation From Primary Site
• Control AC-18(4) — Restrict Configurations By Users
• Control CM-2(2) — Automation Support For Accuracy And Currency
• Control CP-6 — Alternate Storage Site
• Control AC-17(3) — Managed Access Control Points

References

• NIST Computer Security Resource Center — NIST SP 800-53 Rev. 5
• Catalogue identifier: Control CP-11

Topics: network securitybusiness continuitycloud postureconfiguration management