A Cloud Access Security Broker (CASB) is a security control point that sits between users and cloud service providers to enforce organizational security policies. It provides visibility into cloud usage, protects sensitive data, and ensures compliance across SaaS, PaaS, and IaaS environments. Organizations use it to extend on-premises security controls into the cloud.
How It Works
A CASB operates as an intermediary between users and cloud applications. It can function in multiple modes: forward proxy (for managed devices), reverse proxy (for external access), API-based integration (directly with cloud providers), or log-based monitoring. These deployment models allow security teams to monitor and control traffic regardless of user location.
The system inspects traffic and API activity to discover cloud services in use, including unsanctioned “shadow IT” applications. It enforces policies such as data loss prevention (DLP), encryption, tokenization, and access control. For example, it can block uploads of sensitive data to unauthorized apps or require step-up authentication for risky sessions.
It also integrates with identity providers and SIEM/SOAR platforms. By correlating user behavior, device posture, and contextual signals, it applies conditional access rules and generates actionable alerts for security operations teams.
Why It Matters
Cloud adoption decentralizes access to data and services, which increases risk and reduces visibility. Traditional perimeter controls do not apply when users access SaaS applications directly from the internet. A CASB restores governance by enforcing consistent policies across distributed environments.
For DevOps and platform teams, it reduces the risk of data exfiltration, misconfiguration exposure, and compliance violations without blocking cloud innovation. It provides audit trails, usage analytics, and centralized control aligned with zero trust principles.
Key Takeaway
A CASB enforces consistent security and compliance controls across cloud services by acting as a policy enforcement layer between users and the cloud.