What is a Cloud Access Security Broker?

CASB is an enforcement point for accessing cloud services and applications, generally deployed on-premises or cloud-delivered via a collection of services and infrastructural underpinnings—forward and reverse proxies, APIs, and polling for periodic status checks. CASBs are often placed between cloud service consumers and cloud service providers to prevent access and interject enterprise security policies in an attempt to control cloud and SaaS access. For four key capabilities of CASB are visibility, compliance, threat protection, and data loss prevention (DLP).