# NIST SP 800-53 Rev. 5 SC-18(3) — Prevent Downloading And Execution - Source: https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-18-3-prevent-downloading-and-execution - 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-18(3)`·high·Component: **System and Communications Protection** ## What 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. > > — NIST SP 800-53 Rev. 5, Control SC-18(3) ### 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_workflow` evidence 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](https://support.icompaas.com/compliance/nist-sp-800-171-rev-3/3-14-1-flaw-remediation) - [**SOC 2 (2017 TSC) CC7.4** — Incident Response](https://support.icompaas.com/compliance/soc-2-trust-services-criteria/cc7-4-incident-response) - [**CIS Controls v8 5.3** — Disable Dormant Accounts](https://support.icompaas.com/compliance/cis-controls-v8/5-3-disable-dormant-accounts) - [**ISO/IEC 27001:2022 A.5.8** — Information security in project management](https://support.icompaas.com/compliance/iso-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](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-18-1-identify-unacceptable-code-and-take-corrective-actions) - [**Control SC-18(2)** — Acquisition, Development, And Use](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-18-2-acquisition-development-and-use) - [**Control SC-47** — Alternate Communications Paths](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-47-alternate-communications-paths) - [**Control IR-7(2)** — Coordination With External Providers](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/ir-7-2-coordination-with-external-providers) - [**Control SC-15(4)** — Explicitly Indicate Current Participants](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-15-4-explicitly-indicate-current-participants) - [**Control IR-3** — Incident Response Testing](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/ir-3-incident-response-testing) ## 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-18(3)` Topics: governance riskchange managementincident responseendpoint protection ## 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.