A Cloud Access Security Broker (CASB) is a security solution positioned between cloud service users and cloud applications to monitor, manage, and enforce security policies. CASBs provide organizations with visibility into cloud application usage, detect risky behaviors, enforce compliance, and protect sensitive data through features such as authentication, encryption, threat detection, and data loss prevention. By acting as a gatekeeper, CASBs help organizations secure data stored in and accessed through cloud services, ensuring that only authorized users can interact with sensitive information. They are essential for organizations adopting cloud services, as they bridge the security gap between on-premises infrastructure and cloud environments, supporting regulatory compliance and mitigating risks associated with shadow IT.