SC-18(3)·high·Component: System and Communications ProtectionWhat this control requires
Prevent the downloading and execution of unauthorized or untrusted mobile code by blocking disallowed sources and requiring explicit approval before execution. This control supports the Download Control Mechanism capability within the System and Communications Protection family.
In plain English
Prevent the downloading and execution of unauthorized or untrusted mobile code by blocking disallowed sources and requiring explicit approval before execution. In practice, this means you can prove you protection 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-18(3)) and look for objective evidence on the latest two assessment cycles.
How to implement
Incident Response
Runbook. Maintain a runbook keyed by incident type with named roles (IC, comms, scribe), an out-of-band comms channel, and a 72-hour timeline for external notification.
Tabletop. Run a quarterly tabletop exercise (ransomware, insider, supply-chain) and feed gaps back into the runbook.
Endpoint Protection
MDM. Make MDM enrollment a hard gate for device access (Intune compliance + Conditional Access, or Jamf + Okta device trust). Unmanaged devices simply don't get a session token.
EDR. Deploy CrowdStrike / SentinelOne / Defender for Endpoint to every server and laptop; alert on any host that stops sending telemetry for >24h.
Operational checklist
- Protection. Document the trigger, the owner and the cadence.
- Response. Document the trigger, the owner and the cadence.
- Unauthorized. Document the trigger, the owner and the cadence.
- System. Document the trigger, the owner and the cadence.
- Control. Document the trigger, the owner and the cadence.
- Scope: management, system, protection, sources, capability, response, code, mobile code.
Evidence to collect
- Ticketing Workflow.
ticketing_workflowevidence
Workflow metrics (ServiceNow, Jira) show approvals and remediation. Focus: Prevent Downloading And Execution.
Common pitfalls
- Runbooks that name a role but no person, or list a paging channel that no longer exists.
- Pilot MDM rollouts that quietly exclude executives or engineers; carving out the highest-risk users is the most common audit failure.
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 3.14.1 — Flaw Remediation
- SOC 2 (2017 TSC) CC7.4 — Incident Response
- CIS Controls v8 5.3 — Disable Dormant Accounts
- ISO/IEC 27001:2022 A.5.8 — Information security in project management
Related controls in NIST SP 800-53 Rev. 5
- Control SC-18(1) — Identify Unacceptable Code And Take Corrective Actions
- Control SC-18(2) — Acquisition, Development, And Use
- Control SC-47 — Alternate Communications Paths
- Control IR-7(2) — Coordination With External Providers
- Control SC-15(4) — Explicitly Indicate Current Participants
- Control IR-3 — Incident Response Testing
References
- NIST Computer Security Resource Center — NIST SP 800-53 Rev. 5
- Catalogue identifier:
Control SC-18(3)
Topics: governance riskchange managementincident responseendpoint protection