Under the original CMMC 1.0 framework, Level 4 represented an advanced cybersecurity maturity tier designed for contractors handling highly sensitive information or operating in environments at elevated risk of cyberattack. It built on the 110 requirements of NIST SP 800-171 by adding selected practices from NIST SP 800-172. The goal of Level 4 was to require organizations to adopt proactive and adaptive cybersecurity practices, such as more advanced monitoring, threat hunting, and defensive strategies to counter Advanced Persistent Threats (APTs).

With the release of CMMC 2.0 in November 2021, Level 4 was removed as part of an effort to simplify the model and reduce the number of certification tiers. Its intent—to strengthen resilience against sophisticated adversaries—was carried forward into the new CMMC Level 3 (Expert), which now incorporates the enhanced security requirements of NIST SP 800-172.