Cloud Access Security Broker (CASB)
Secure and monitor cloud application access while enforcing organizational security policies.
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Last Updated date: June 2026
A Cloud Access Security Broker (CASB) is a security enforcement layer positioned between enterprise users and cloud services — SaaS, IaaS, and PaaS — that monitors activity, applies security policies, and protects data regardless of where users are connecting from. Where Identity and Access Management (IAM) controls who gets in, a CASB governs what happens after they're in and how data moves.
Quick Summary
| Field | Detail |
|---|---|
| Category | Cloud Security / Data Protection / Identity-Adjacent Control |
| Related to | SASE, Zero Trust, DLP, IAM, Shadow IT |
| Primary use | Cloud visibility, data loss prevention, threat protection, compliance enforcement |
| Key benefit | Unified security policy across all cloud apps — including apps IT didn't approve |
The Problem CASB Was Built to Solve
Enterprise data no longer lives in the data center. It moves through Salesforce, Google Drive, Microsoft 365, Slack, and dozens of other SaaS applications, many of which IT didn't choose, approve, or even know about.
Traditional perimeter security has no visibility into this traffic. Native cloud app security controls are inconsistent and siloed. The result: employees upload sensitive data to unauthorized services, share files without restriction, and access corporate apps from unmanaged personal devices, none of it visible to the security team.
A CASB closes that gap by creating a single, policy-enforced control point across every cloud service, sanctioned or not.
What a CASB Actually Does: The Four Pillars
1. Visibility and Shadow IT Discovery: A CASB identifies every cloud application in use across the organization, including apps that IT never approved. It maps user activity, data volume, and risk level per app, giving security teams a complete picture of cloud usage rather than a partial one.
2. Data Security and DLP: A CASB enforces data loss prevention (DLP) policies directly within cloud workflows. It can detect when sensitive data, such as PII, financial records, and intellectual property, is being uploaded to unauthorized destinations, shared externally, or downloaded to unmanaged devices, and block or alert in real time.
3. Threat Protection: CASBs scan files and traffic for malware, detect anomalous user behavior (unusual download volumes, access from unexpected locations), and flag compromised accounts, often by integrating with UEBA (User and Entity Behavior Analytics) signals or identity governance platforms.
4. Compliance and Access Control: CASBs enforce authentication requirements, conditional access policies (device trust, location, risk score), and data residency rules that satisfy regulatory frameworks including GDPR, HIPAA, and PCI-DSS. Every access and data event is logged for audit.
How CASBs Are Deployed
The deployment model determines what a CASB can see and enforce:
API-Based CASB: Connects directly to cloud providers via their native APIs. Provides deep visibility into data at rest, user activity, file sharing configurations, and misconfigurations, without sitting in the traffic path. Low performance impact; best for sanctioned SaaS apps with API support. Does not inspect real-time traffic.
Forward Proxy: Sits between users (on-premises or remote) and cloud services, intercepting outbound traffic in real time. Best for managed devices and enforcing policy before data reaches the cloud app. Requires device-level proxy configuration.
Reverse Proxy: Sits between the cloud application and the user, without requiring endpoint configuration. Particularly effective for unmanaged devices (contractors, personal devices) accessing corporate SaaS apps. Enforces session-level controls without installing a client.
Most enterprise deployments use a combination of API-based and proxy modes to cover both data at rest and real-time traffic across managed and unmanaged endpoints.
Key Capabilities at a Glance
- Shadow IT discovery
Full inventory of cloud apps in use, risk-rated by category - Data loss prevention
Policy enforcement on uploads, downloads, and external sharing - Malware scanning
Inspects files moving into and out of cloud storage and collaboration tools - Conditional access
Enforces MFA, device trust, and location-based policies per app - Behavioral analytics
Detects anomalous activity patterns consistent with insider threat or account compromise - Encryption and tokenization
protects sensitive data fields in transit to or within cloud apps - Compliance reporting
generates access and data-event logs aligned to GDPR, HIPAA, SOC 2, and PCI-DSS audit requirements
Extend Your Identity Controls Into the Cloud
IAM controls who gets access. CASB governs what they can do once they're in. See how Tech Prescient integrates with CASB solutions to enforce unified access policy, automate provisioning, and maintain audit-ready logs across your entire SaaS estate.
CASB in the Enterprise Security Stack
CASB and IAM: Complementary, Not Competing
IAM determines access entitlements and enforces authentication. CASB enforces data and behavior policy within cloud sessions after authentication. The two controls operate at different layers, and gaps appear when only one is in place. IAM without CASB leaves data movement uncontrolled. CASB without IAM lacks a reliable identity foundation for its policies.
CASB and SASE
Secure Access Service Edge (SASE) architectures converge networking and security into a unified cloud-delivered service. CASB is a core security function within SASE, typically alongside Secure Web Gateway (SWG), Zero Trust Network Access (ZTNA), and SD-WAN. Organizations building toward SASE often start with CASB as the cloud security control layer.
CASB and Zero Trust
Zero Trust requires continuous verification, not a one-time access decision. CASBs support Zero Trust by enforcing per-session policy based on dynamic signals: device posture, user behavior, data sensitivity, and location. A user with valid credentials on an unmanaged device in an unusual location can be granted limited access rather than full access, a Zero Trust access decision enforced at the CASB layer.
Industry Applications
Financial Services
Banks and asset managers use CASBs to enforce data residency rules (ensuring customer financial data doesn't leave approved regions), control file sharing in collaboration platforms, and detect anomalous access consistent with insider trading or account compromise. CASB audit logs directly support SEC, FINRA, and SOX compliance requirements.
Healthcare
Hospitals and health systems use CASBs to prevent PHI from being uploaded to unauthorized cloud storage, enforce device trust for clinical staff accessing EHR integrations, and maintain HIPAA-compliant audit trails across SaaS applications that weren't designed with healthcare compliance in mind.
SaaS and Technology Companies
Fast-scaling tech companies use CASBs to manage the sprawl of developer tools, collaboration apps, and cloud infrastructure while maintaining visibility for SOC 2 audits. Shadow IT discovery is particularly valuable in these environments, where employees adopt new tools faster than IT can formally evaluate them.
CASB vs. Related Technologies
| CASB | Secure Web Gateway (SWG) | ZTNA | |
|---|---|---|---|
| Primary focus | Cloud app visibility + data security | Web traffic filtering + URL control | Application access based on identity + context |
| Coverage | SaaS, IaaS, PaaS | Internet traffic broadly | Internal and private applications |
| Data protection | Yes (DLP, encryption) | Limited | No |
| Shadow IT discovery | Yes | Partial | No |
| Where it fits | Cloud security layer | Network security layer | Access control layer |
These tools are increasingly converging in SASE platforms, but understanding their distinct roles helps in evaluating what each control actually covers.
Implementation Considerations
1. Start with discovery, not enforcement
Before applying blocking policies, use the CASB in monitoring mode to build a complete picture of cloud app usage. Enforcing policy against apps you don't fully understand yet leads to user disruption and IT backlash.
2. Integrate with your identity platform first
CASB policies are only as reliable as the identity signals they're based on. Connecting the CASB to your IAM or identity governance platform ensures that role changes, offboarding events, and access policy updates propagate correctly into CASB enforcement.
3. Prioritize high-risk data categories
Focus initial DLP policies on the data types that carry compliance or breach consequences, PII, financial data, health records, and source code. Broad policies applied too early generate noise and reduce trust in the system.
4. Plan for unmanaged device scenarios
Contractors, partners, and hybrid workers on personal devices are a common coverage gap. Reverse proxy deployment or browser isolation should be part of the architecture conversation for any organization with significant unmanaged device usage.
5. Treat CASB as a live signal source, not a static control
CASB generates behavioral and data telemetry that should feed into your SIEM, identity governance platform, and incident response workflows. A CASB that logs but doesn't integrate is a compliance tool. A CASB that feeds signals into your broader security stack is a threat detection capability.
Frequently Asked Questions
CASB stands for Cloud Access Security Broker. The term "broker" refers to its role as an intermediary; it sits between users and cloud services to broker security policy between them.
No. A traditional firewall controls network perimeter traffic. A CASB controls activity within cloud applications; it understands application-layer context (who is doing what with which data) rather than just blocking or allowing traffic at the network level.
DLP (Data Loss Prevention) is a policy capability. CASB is a platform that can enforce DLP, among other controls. A CASB can include DLP as one of its functions; a standalone DLP tool typically covers endpoints or email rather than cloud apps specifically.
Yes, they address different problems. IAM governs who gets access and under what conditions. CASB governs what users do inside cloud sessions and how data moves. An organization with strong IAM but no CASB has good access control but no visibility into data behavior in the cloud.
CASB provides continuous, session-level policy enforcement, a core Zero Trust requirement. It evaluates dynamic signals (device health, behavior, data sensitivity) to make per-request access decisions within cloud apps, rather than treating a successful login as blanket authorization.
The four pillars are visibility (discovering cloud usage), data security (DLP and encryption), threat protection (malware and behavioral anomaly detection), and compliance (enforcing regulatory controls and audit logging). Most enterprise CASB solutions address all four, though depth varies by vendor.
Related Terms
Identity and Access Management (IAM)
Zero Trust Security
Data Loss Prevention (DLP)
Secure Access Service Edge (SASE)
Shadow IT
Zero Trust Network Access (ZTNA)
User and Entity Behavior Analytics (UEBA)
Conditional Access