Power BI developers can ensure data security by implementing Row-Level Security (RLS), which restricts access to specific data based on user roles. They should also integrate Power BI with Azure Active Directory for secure authentication and Single Sign-On (SSO) functionality. Using secure data gateways for cloud-to-on-premise data connections is crucial for protecting data in transit. Additionally, Power BI developers should apply sensitivity labels to datasets, ensuring compliance with organizational and regulatory standards. Regular security audits and maintaining up-to-date permissions are key to ensuring continuous data protection.