This post gives a practical, implementation-focused checklist to meet FAR 52.204-21 and CMMC 2.0 Level 1 control AC.L1-B.1.IV — the requirement to control what information is posted on public websites — with step-by-step actions, technical controls, audit evidence examples, and real-world scenarios for a small business responsible for federal contracts.
Understanding the requirement and key objectives
FAR 52.204-21 requires contractors to safeguard contractor information systems, and CMMC 2.0 Level 1 Control AC.L1-B.1.IV specifically addresses controlling information posted publicly so that Controlled Unclassified Information (CUI) and other sensitive data are not exposed on public websites. The objective is simple: prevent accidental or intentional posting of CUI, PII, or other sensitive operational data to any publicly accessible web resource (marketing sites, blogs, knowledge bases, file shares, CDN buckets, or staging sites).
Step-by-step compliance checklist for Compliance Framework
1) Inventory and classify all web assets and content sources
Start by cataloguing every public-facing asset: primary website, microsites, marketing pages, blogs, GitHub Pages, content delivery networks (CDNs), storage buckets (S3, Azure Blob), third-party widgets, and partner portals. For each asset record owner, hosting provider, CMS, domain/subdomain, and content sources (CMS files, user uploads, API endpoints). Tag content sources in your inventory with classification labels (Public, Internal, CUI, PII) and mark any content that must never be public. This inventory is a core Compliance Framework artifact you will maintain and present during assessments.
2) Policy, governance and publishing workflow
Create a written web content policy that explicitly states what cannot be posted publicly (CUI, contract numbers, SSNs, financial data, technical drawings). Implement a mandatory approval workflow: content must be reviewed by a designated approver before publication. Practical tools: enforce approval gates in your CMS (WordPress, Drupal, Contentful) or use a ticketing system (Jira, GitHub PRs) where the approver must sign off. Maintain records of approvals, reviewer names, timestamps, and links to the final published page as compliance evidence.
3) CMS, hosting and access-control technical controls
Enforce least privilege in CMS and hosting accounts — assign roles (Author, Editor, Publisher, Admin) and remove default accounts. Enable multi-factor authentication for all admin users and require unique corporate accounts rather than shared credentials. For static hosting and object storage (e.g., S3), ensure buckets are not public by default and use bucket policies or signed URLs for any restricted documents. Disable directory listing, lock down FTP/SFTP, and ensure HTTPS with HSTS. For third-party plugins or integrations, maintain a whitelist and require security reviews prior to deployment.
4) Automated scanning and pre-publish checks
Automate content scanning in the publishing pipeline. Examples: integrate regex-based checks (for SSNs \b\d{3}-\d{2}-\d{4}\b, credit card patterns, or custom CUI markers like "CUI" or "CONTROLLED") and DLP APIs (Microsoft Purview, Google DLP, or open-source scanners) into pre-publish hooks. For code and static sites, add pre-commit and CI checks that scan new content for patterns and deny merges or deployments if violations are found. Use file type restrictions and MIME checks to block potentially sensitive attachments (e.g., .docx/.xlsx/.pdf containing CUI) unless explicitly approved and served from an authenticated area.
5) Runtime protections, monitoring and logging
Deploy logging and monitoring to detect unexpected exposures: enable web server and CDN access logging, configure CloudTrail or equivalent for object store access, and forward logs to a centralized system (SIEM, Splunk, ELK). Implement file integrity monitoring on web roots and watchers on S3 buckets to alert if new files are added to public locations. Use a Web Application Firewall (WAF) to block suspicious uploads and to prevent directory traversal. Retain logs and scan reports as evidence of ongoing control and map log retention to contract/audit requirements.
Real-world small business scenarios and practical examples
Example 1: Marketing accidentally uploads a technical contract excerpt to the press kit. Fixes: add a mandatory review step in CMS, scan uploaded docs for CUI markers and block immediate publication until cleared. Example 2: Development pushes a build that contains a /staging endpoint with internal APIs exposed. Fixes: ensure staging is not publicly accessible (use VPN or IP allowlist), and integrate CI checks to strip or secure debug endpoints before publishing. Example 3: An S3 bucket configured for website hosting contains a directory of invoices. Fixes: set bucket policy to private, move sensitive docs to an authenticated application or use presigned URLs with short TTL, and run an S3 inventory scan to identify and remediate exposed objects.
Compliance tips, evidence to collect, and risks of non-compliance
Compliance tips: (1) Maintain an evidence package: content inventory spreadsheet, policies, workflow screenshots, CMS role configuration, scan reports, approval tickets, training records, and access logs. (2) Run quarterly content sweeps with automated tools and a manual review of high-risk pages. (3) Train marketing, HR, and devs on examples of CUI and red flags. Risks of not implementing these controls include immediate CUI exposure, loss of federal contracts, contractual penalties, reputational damage, and potential regulatory action — plus the practical impact of remediation costs and incident response if sensitive files are leaked publicly.
Conclusion
To meet FAR 52.204-21 and CMMC 2.0 AC.L1-B.1.IV you need a defensible mix of policy, process, and technical controls: inventory all web assets, enforce an approval workflow, harden CMS/hosting access, automate pre-publish scanning, and monitor runtime activity while retaining evidence for audits. For a small business these steps are scalable and affordable — start with a simple inventory and policy, add automated scanning in your publishing pipeline, and gradually tighten access and monitoring to build a repeatable Compliance Framework that demonstrably prevents public posting of CUI.
