A Cloud Access Security Broker (CASB, pronounced KAZ-bee) is an on-premises or cloud-based policy enforcement point placed between cloud service consumers and cloud service providers (CSPs) to monitor cloud-related activity and to apply security, compliance, and governance rules related to the use of cloud based resources. A CASB lets an organization extend to the cloud the same sorts of controls it would apply to on-premises infrastructure, and can combine different types of policy enforcements, such as:
user credential authentication so access is provided only to approved cloud services
data protection through encryption, tokenization, or other means so sensitive information is not exposed in cloud services or to CSPs
cloud service activity monitoring so user and entity behavior can be logged, flagged, and analyzed for anomalous usage patterns or compromised credentials
data loss prevention (DLP) so sensitive information cannot leave the organization’s network, and
malware detection and remediation so sensitive information cannot enter the organization’s network.
The purpose of a CASB is thus to improve an organization’s ability to take advantage of cloud services safely and securely. A CASB can be thought of as a “security node” through which access to an organization’s cloud services is controlled. As a component of an organization’s security infrastructure, it complements, rather than replaces, technologies such as enterprise and web application firewalls, IDaaS (IDentity as a Service), and secure web gateways (SWGs).
The increasing importance of CASBs parallels the wider adoption of cloud services and BYOD (“Bring Your Own Device”) policies that permit personal laptops, smartphones, tablets, and other unmanaged devices onto the network. The use of CASBs to control some or all of an organization’s cloud services is expanding and it is expected that adoption by larger enterprises will triple, from 20% in 2018 to 60% by 2022 (Gartner, 2018). Over a similar period, the cloud security market as a whole is predicted to rise to around $112B by 2023 (Forrester, 2017).