The best way to ensure ongoing control effectiveness is to measure trends in control performance. This will help to monitor and evaluate how well the controls are achieving their objectives, and to identify any deviations or anomalies that may indicate control failures or weaknesses. Measuring trends in control performance also helps to provide feedback and assurance to the stakeholders and decision makers, and to support continuous improvement andoptimization of the control environment. Establishing policies and procedures, periodically reviewing control design, and obtaining management control attestations are good practices, but they are not the best way to ensure control effectiveness. References = Risk and Information Systems Control Study Manual, 7th Edition, Chapter 3, Section 3.1.1.2, page 1071

1: ISACA Certified in Risk and Information Systems Control (CRISC®) Exam Guide, Answer to Question 650.