# NIST SP 800-53 Rev. 5 SC-7(5) — Deny By Default -- Allow By Exception - Source: https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-7-5-deny-by-default-allow-by-exception - 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-7(5)`·high·Component: **System and Communications Protection** ## What this control requires > Deny network communications traffic by default and allow only essential, approved connections by exception at managed interfaces or for organization-defined systems, ensuring secure inbound and outbound traffic control. This control supports the Firewall capability within the System and Communications Protection family. > > — NIST SP 800-53 Rev. 5, Control SC-7(5) ### In plain English Deny network communications traffic by default and allow only essential, approved connections by exception at managed interfaces or for organization-defined systems, ensuring secure inbound and outbound traffic control. 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. 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-7(5)) 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 - **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. - **Protection.** Document the trigger, the owner and the cadence. - **System.** Document the trigger, the owner and the cadence. - **Scope:** management, organization, system, only, protection, configuration, capability, systems. ## 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: Deny By Default -- Allow By Exception. ## 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) - [**BSI C5:2020 COS-05** — Networks for administration](https://support.icompaas.com/compliance/bsi-c5-2020/cos-05-networks-for-administration) - [**ISO/IEC 27001:2022 A.8.22** — Segregation of networks](https://support.icompaas.com/compliance/iso-27001-2022/a-8-22-segregation-of-networks) - [**CIS Controls v8 4.2** — Establish and Maintain a Secure Configuration Process for Network Infrastructure](https://support.icompaas.com/compliance/cis-controls-v8/4-2-establish-and-maintain-a-secure-configuration-process-for-network-infrastructure) ## Related controls in NIST SP 800-53 Rev. 5 - [**Control SC-10** — Network Disconnect](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-10-network-disconnect) - [**Control SC-7(8)** — Route Traffic To Authenticated Proxy Servers](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-7-8-route-traffic-to-authenticated-proxy-servers) - [**Control SC-7(16)** — Prevent Discovery Of System Components](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-7-16-prevent-discovery-of-system-components) - [**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 SC-7(29)** — Separate Subnets To Isolate Functions](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-7-29-separate-subnets-to-isolate-functions) - [**Control SC-28(2)** — Offline Storage](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-28-2-offline-storage) ## 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-7(5)` Topics: network securitycloud 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.