NIST SP 800-53 Rev. 5·Control SC-35·high·Component: System and Communications Protection

What this control requires

Include system components that proactively identify network-based malicious code or malicious websites. Unlike decoys, these components actively probe networks, including the Internet, to detect malicious code on external websites. Virtualization is commonly used to isolate discovered malicious code and prevent it from infecting organizational systems. This control supports the Malicious Code Detection System capability within the System and Communications Protection family.
— NIST SP 800-53 Rev. 5, Control SC-35

In plain English

Include system components that proactively identify network-based malicious code or malicious websites. In practice, this means you can prove you security system-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-35) and look for objective evidence on the latest two assessment cycles.

How to implement

Secure Development

Pipeline. Require code review, SAST (Semgrep / Snyk Code), SCA (Dependabot / Renovate), secret-scanning and IaC scanning in the merge pipeline.

Branch protection. Protected branches enforce reviews, signed commits and passing CI before merge; document the protection rules as the control evidence.

Code Review Testing

Pipeline. Require at least one human reviewer plus passing CI (lint, type, unit, security scan) before merge — protected branches enforce this.

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.
  • Detection. Document the trigger, the owner and the cadence.
  • Network. Document the trigger, the owner and the cadence.
  • Review. Document the trigger, the owner and the cadence.
  • Protection. Document the trigger, the owner and the cadence.
  • Scope: system, application, virtualization, protection, review, components, capability, networks.

Evidence to collect

  • Code Repo Scan. Source-control evidence — branch protection, required reviewers, CI status, SCA / SAST reports.

Source control pipelines (GitHub, GitLab) enforce SDLC guardrails. Focus: External Malicious Code Identification.

Common pitfalls

  • CI security checks set to warn-only; the merge button is faster than the security feedback.
  • Default-allow egress rules; East-West traffic with no segmentation; jump hosts on the public internet with password auth.

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.

Related controls in NIST SP 800-53 Rev. 5

References

Topics: application securitysecure developmentcode review testingdevsecopsnetwork security