Monitor security controls on an ongoing basis to ensure the continued effectiveness of the controls. 

Assessment Objective 

[a]: Determine if security controls in the system are monitored on an ongoing basis to ensure the continued effectiveness of the controls. 

Spirit of the Control and Objectives 

This control ensures that organizations continuously monitor the effectiveness of their security controls, allowing them to detect changes, identify security weaknesses, and proactively respond to emerging threats. Unlike periodic assessments, ongoing monitoring provides real-time visibility into security control performance, ensuring that protections remain effective as system configurations, user activity, and threat landscapes evolve. 

Continuous monitoring helps organizations maintain compliance with NIST SP 800-171 requirements, reduce security risks, and strengthen their overall cybersecurity posture by ensuring that controls operate as expected in dynamic environments. 

Common Ways to Meet the Control 

• Implement a continuous monitoring program: Establish a structured approach for tracking, reviewing, and validating security controls at regular intervals. A tool such as ASCERA can help provide a foundation for such a program, leveraging data from a variety of sources to help determine the effectiveness of the control(s). 

• Use security information and event management (SIEM) solutions: Deploy SIEM tools to aggregate logs, analyze security events, and detect anomalies in real time. 

• Automate security monitoring: Utilize endpoint detection and response (EDR), vulnerability scanning, and intrusion detection/prevention systems (IDS/IPS) to monitor security controls. 

• Conduct regular security audits and control reviews: Perform internal security audits, risk assessments, and automated control checks to verify control effectiveness. 

• Leverage configuration management and change control processes: Continuously track system modifications, updates, and patches to ensure they do not compromise security controls. 

• Monitor user activity and access logs: Use privileged access monitoring, behavioral analytics, and alerting mechanisms to identify potential security risks. 

• Document and report monitoring activities: Maintain logs, reports, and audit trails demonstrating that security controls are actively monitored and assessed. 

How We Interpret the Control 

This control requires organizations to adopt a proactive approach to security control validation through continuous tracking, real-time security event analysis, and automated monitoring tools. Unlike CA.L2-3.12.1, which focuses on periodic assessments, this control mandates ongoing monitoring of security controls to detect and mitigate risks as they emerge. 

This control aligns closely with CA.L2-3.12.2, which ensures that security deficiencies identified through monitoring activities are addressed using Plans of Action and Milestones (POA&Ms). 

What an Assessor Looks For 

• Documented security monitoring policies and procedures, detailing how controls are continuously evaluated. 

• Logs and records demonstrating ongoing security control monitoring, including SIEM reports, IDS/IPS alerts, and vulnerability scans. 

• Evidence of automated security monitoring tools, showing real-time detection and reporting of security control effectiveness. 

• Incident response reports or audit findings, indicating how issues identified during security monitoring are managed and resolved. 

• Change management records, ensuring that security control effectiveness is maintained through system updates and modifications. 

• Periodic reports on control effectiveness, demonstrating management oversight and continuous security improvement. 

Additional Comments 

Continuous Monitoring vs. Periodic Assessments Summary 

While both ongoing monitoring (CA.L2-3.12.3) and periodic security assessments (CA.L2-3.12.1) serve to validate the effectiveness of security controls, they differ in approach and frequency. Periodic assessments are scheduled evaluations (e.g., annually or quarterly) that provide a snapshot of security effectiveness at a specific point in time. In contrast, ongoing monitoring is a continuous process, leveraging real-time security tools, automated alerts, and log analysis to detect changes and respond to risks immediately. Together, these approaches provide a comprehensive security management framework that ensures long-term compliance, risk reduction, and system resilience.