NIST SP 800-171 Rev.2 / CMMC 2.0 Level 2 control RA.L2-3.11.2 requires organizations to scan for vulnerabilities in organizational systems and applications — and to do so in a manner that supports both continuous monitoring and ad-hoc (on-demand) discovery. This post gives practical, step-by-step advice for configuring Nessus (and Tenable agents/console where applicable) so a small business can meet that requirement and produce audit-ready evidence.
\n\nThe Compliance Framework requires that your environment be continuously assessed for vulnerabilities and that you can perform on-demand scans when changes or incidents occur. In practice you must: 1) establish a regular continuous monitoring capability, 2) be able to launch immediate scans during incidents or after changes, and 3) collect and retain scan artifacts (policies, schedules, reports, remediation tracking) as evidence. Map assets that store/process CUI or sensitive mission data and ensure they are prioritized in scan scopes and reports.
\n\nFor small businesses, use a combination of Nessus (scanner) and Tenable Agents or Tenable.io/Tenable.sc as available: - Nessus Professional or Nessus Manager as the primary scanner for network scans; - Tenable Agents deployed on endpoints for continuous local scanning (useful behind NAT, remote workers, or roaming laptops); - A central Tenable console (Tenable.io or Tenable.sc) if you need schedule orchestration, asset tracking, and centralized reporting. Ensure you keep an asset inventory (IP, hostnames, owner, CUI flag) in the console to map scan results to Compliance Framework control sets.
\n\nCreate explicit scan policies named for compliance and audit clarity (e.g., \"CF-RAL2-Credentialed-Patch-Audit\" and \"CF-RAL2-External-Internet-Scan\"). Key settings: enable credentialed checks (Windows: SMB/WinRM with a service account; Linux/Unix: SSH key or username+password with sudo configured), enable Patch Audit and Audit Files plugins, set Safe Checks on if you have sensitive systems, and run a full TCP/UDP port range scan (1-65535) for critical hosts but restrict to common ports (1-1024, plus apps ports) for lower impact. In Advanced settings adjust \"Max simultaneous checks per host\" to 1–3 for production servers to reduce load and set \"Network Timeout\" to 30s–60s depending on network reliability. Use SSH keys for Linux and a dedicated domain service account for Windows with the least privileges required to enumerate patches and installed apps.
\n\nContinuous monitoring options: 1) Agent-based continuous scans — configure Tenable Agents to run continuously or at a short interval (for small organizations, set agents to run hourly or every 4–24 hours depending on resources) and report to the central console; 2) Regularly scheduled authenticated network scans — schedule internal vulnerability scans nightly or weekly for servers and daily for critical CUI systems; 3) Passive monitoring — where available, use Nessus Network Monitor (or equivalent) for near-real-time detection of new hosts/services. For RA.L2-3.11.2 you must show the organization actively monitors on an ongoing basis; agents provide the clearest \"continuous\" posture because they scan locally and report immediately after updates.
\n\nDefine and document a standard operating procedure (SOP) for ad-hoc scans: when a change occurs (new system, patch failed) or an incident triggers suspicion, authorized personnel should be able to run targeted on-demand scans. Configure templates for rapid use: \"IR-Quick-Scan\" (top 100 plugins + exploit checks disabled), \"IR-Deep-Scan\" (credentialed + patch audit). Keep pre-created asset lists (CUI-Servers, Remote-Laptops) so on-demand scans can be launched in <2 minutes. Integrate result exports with your ticketing system (JIRA, ServiceNow) with automatic creation of remediation tickets including CVE IDs, plugin IDs, and suggested fixes to demonstrate remediation tracking for auditors.
\n\nFor each scheduled and on-demand scan, export and retain: scan policy (JSON/XML), schedule settings, scan results (PDF/CSV), executive summary (showing counts by severity), and remediation tickets. In the Tenable console tag assets as \"CUI\" or \"in-scope\" and create saved reports filtered to those tags for RA.L2-3.11.2 evidence. Correlate findings to NIST 800-171 control language (e.g., map high-risk CVEs affecting CUI systems to RA.L2-3.11.2) in an evidence binder. Retain logs for the retention period required by your Compliance Framework — typically 12–24 months — and ensure timestamped scan IDs are preserved for audit.
\n\nExample 1: Small engineering firm with 15 workstations and 3 servers hosting CUI. Deploy Tenable Agents on all endpoints, configure hourly agent scans with credentialed checks on servers, and schedule a nightly authenticated Nessus internal scan for servers. Use a weekly external Nessus scan for public-facing services. Example 2: Managed service provider hosting contractor systems — use Tenable.sc to centralize many client scanners, build per-client asset tags, create automated reports delivered monthly, and maintain remediation ticketing to show a closed-loop process. These straightforward setups balance continuous coverage and operational cost.
\n\nFailing to implement continuous and on-demand scanning exposes you to undetected vulnerabilities, ransomware, data exfiltration, and potential loss of DoD contracts for noncompliance. Auditors will look for consistent scan schedules, credentialed scanning evidence, and documented remediation. Best practices: maintain a written scanning policy, limit scan scope to avoid service disruption, use credentialed scans for accurate patch-level results, exclude critical production windows or use lower-impact settings for sensitive systems, and regularly validate that agents/reporting are functioning (test with a simulated change). Maintain a remediation SLA (e.g., critical = 7 days, high = 30 days) and demonstrate tracking.
\n\nSummary: Configure Nessus and Tenable agents to combine continuous local scans with scheduled network scans and fast on-demand templates, enable credentialed checks and patch audits, throttle scans for safety, and centralize reporting with asset tagging to meet RA.L2-3.11.2. Document policies, collect and retain evidence, and integrate results into remediation workflows so your small business can demonstrably meet the Compliance Framework scanning requirements while minimizing operational disruption.
", "plain_text": "NIST SP 800-171 Rev.2 / CMMC 2.0 Level 2 control RA.L2-3.11.2 requires organizations to scan for vulnerabilities in organizational systems and applications — and to do so in a manner that supports both continuous monitoring and ad-hoc (on-demand) discovery. This post gives practical, step-by-step advice for configuring Nessus (and Tenable agents/console where applicable) so a small business can meet that requirement and produce audit-ready evidence.\n\nUnderstand the objective and mapping to \"Compliance Framework\"\nThe Compliance Framework requires that your environment be continuously assessed for vulnerabilities and that you can perform on-demand scans when changes or incidents occur. In practice you must: 1) establish a regular continuous monitoring capability, 2) be able to launch immediate scans during incidents or after changes, and 3) collect and retain scan artifacts (policies, schedules, reports, remediation tracking) as evidence. Map assets that store/process CUI or sensitive mission data and ensure they are prioritized in scan scopes and reports.\n\nImplementation: architecture and components\nFor small businesses, use a combination of Nessus (scanner) and Tenable Agents or Tenable.io/Tenable.sc as available: - Nessus Professional or Nessus Manager as the primary scanner for network scans; - Tenable Agents deployed on endpoints for continuous local scanning (useful behind NAT, remote workers, or roaming laptops); - A central Tenable console (Tenable.io or Tenable.sc) if you need schedule orchestration, asset tracking, and centralized reporting. Ensure you keep an asset inventory (IP, hostnames, owner, CUI flag) in the console to map scan results to Compliance Framework control sets.\n\nScan policy and credentialing (technical detail)\nCreate explicit scan policies named for compliance and audit clarity (e.g., \"CF-RAL2-Credentialed-Patch-Audit\" and \"CF-RAL2-External-Internet-Scan\"). Key settings: enable credentialed checks (Windows: SMB/WinRM with a service account; Linux/Unix: SSH key or username+password with sudo configured), enable Patch Audit and Audit Files plugins, set Safe Checks on if you have sensitive systems, and run a full TCP/UDP port range scan (1-65535) for critical hosts but restrict to common ports (1-1024, plus apps ports) for lower impact. In Advanced settings adjust \"Max simultaneous checks per host\" to 1–3 for production servers to reduce load and set \"Network Timeout\" to 30s–60s depending on network reliability. Use SSH keys for Linux and a dedicated domain service account for Windows with the least privileges required to enumerate patches and installed apps.\n\nContinuous scanning strategy\nContinuous monitoring options: 1) Agent-based continuous scans — configure Tenable Agents to run continuously or at a short interval (for small organizations, set agents to run hourly or every 4–24 hours depending on resources) and report to the central console; 2) Regularly scheduled authenticated network scans — schedule internal vulnerability scans nightly or weekly for servers and daily for critical CUI systems; 3) Passive monitoring — where available, use Nessus Network Monitor (or equivalent) for near-real-time detection of new hosts/services. For RA.L2-3.11.2 you must show the organization actively monitors on an ongoing basis; agents provide the clearest \"continuous\" posture because they scan locally and report immediately after updates.\n\nOn-demand scans and incident response\nDefine and document a standard operating procedure (SOP) for ad-hoc scans: when a change occurs (new system, patch failed) or an incident triggers suspicion, authorized personnel should be able to run targeted on-demand scans. Configure templates for rapid use: \"IR-Quick-Scan\" (top 100 plugins + exploit checks disabled), \"IR-Deep-Scan\" (credentialed + patch audit). Keep pre-created asset lists (CUI-Servers, Remote-Laptops) so on-demand scans can be launched in \n\nReporting, evidence collection, and compliance mapping\nFor each scheduled and on-demand scan, export and retain: scan policy (JSON/XML), schedule settings, scan results (PDF/CSV), executive summary (showing counts by severity), and remediation tickets. In the Tenable console tag assets as \"CUI\" or \"in-scope\" and create saved reports filtered to those tags for RA.L2-3.11.2 evidence. Correlate findings to NIST 800-171 control language (e.g., map high-risk CVEs affecting CUI systems to RA.L2-3.11.2) in an evidence binder. Retain logs for the retention period required by your Compliance Framework — typically 12–24 months — and ensure timestamped scan IDs are preserved for audit.\n\nPractical small-business examples and scenarios\nExample 1: Small engineering firm with 15 workstations and 3 servers hosting CUI. Deploy Tenable Agents on all endpoints, configure hourly agent scans with credentialed checks on servers, and schedule a nightly authenticated Nessus internal scan for servers. Use a weekly external Nessus scan for public-facing services. Example 2: Managed service provider hosting contractor systems — use Tenable.sc to centralize many client scanners, build per-client asset tags, create automated reports delivered monthly, and maintain remediation ticketing to show a closed-loop process. These straightforward setups balance continuous coverage and operational cost.\n\nRisks of non-implementation and compliance tips\nFailing to implement continuous and on-demand scanning exposes you to undetected vulnerabilities, ransomware, data exfiltration, and potential loss of DoD contracts for noncompliance. Auditors will look for consistent scan schedules, credentialed scanning evidence, and documented remediation. Best practices: maintain a written scanning policy, limit scan scope to avoid service disruption, use credentialed scans for accurate patch-level results, exclude critical production windows or use lower-impact settings for sensitive systems, and regularly validate that agents/reporting are functioning (test with a simulated change). Maintain a remediation SLA (e.g., critical = 7 days, high = 30 days) and demonstrate tracking.\n\nSummary: Configure Nessus and Tenable agents to combine continuous local scans with scheduled network scans and fast on-demand templates, enable credentialed checks and patch audits, throttle scans for safety, and centralize reporting with asset tagging to meet RA.L2-3.11.2. Document policies, collect and retain evidence, and integrate results into remediation workflows so your small business can demonstrably meet the Compliance Framework scanning requirements while minimizing operational disruption." }, "metadata": { "description": "Step-by-step guidance to configure Nessus (and Tenable agents) for continuous and on-demand vulnerability scans that meet NIST SP 800-171 Rev.2 / CMMC 2.0 Level 2 RA.L2-3.11.2 requirements, including policy settings, credentialing, scheduling, reporting, and evidence collection.", "permalink": "/how-to-configure-nessus-for-continuous-and-on-demand-scans-to-satisfy-nist-sp-800-171-rev2-cmmc-20-level-2-control-ral2-3112.json", "categories": [], "tags": [] } }