Security control effectiveness refers to the ability to verify whether implemented security measures, such as firewalls, endpoint detection and response (EDR), or access controls, are actually working as intended to prevent, detect, or mitigate real-world cyber threats. This involves regular testing, monitoring, and assessment to ensure that these controls are not only present but are actively stopping or reducing the impact of security incidents. Effective controls help organizations identify gaps, improve their security posture, and comply with regulatory requirements. Measuring effectiveness may include penetration testing, red teaming, or automated validation tools.