A Cloud Access Security Broker (CASB) is a security tool that acts as an intermediary between cloud service users and cloud applications, providing a centralized approach to enforce security policies. CASBs help organizations protect sensitive data, manage user activity, and secure access to cloud resources by offering features like data loss prevention (DLP), threat protection, visibility, and compliance management. By providing a layer of control over data and users across multiple cloud services, CASBs enable organizations to safely adopt cloud technologies while maintaining visibility and control over their data.