Cloud Access Security Broker (CASB): Controlling the Chaos of Cloud Apps

The average enterprise today uses hundreds of cloud services — from collaboration tools like Slack and Microsoft 365 to CRMs like Salesforce and marketing platforms like HubSpot. While these tools improve productivity, they also open up new vulnerabilities and blind spots.

How do you protect data when it no longer resides in your network?

That’s where the Cloud Access Security Broker (CASB) comes in — a powerful layer of control between your users and the cloud.

What Is a CASB?

A Cloud Access Security Broker (CASB) is a security solution that sits between users and cloud service providers to enforce security policies, visibility, compliance, and threat protection.

CASBs act as the “traffic cop” for cloud access — helping security teams:

• Discover shadow IT

• Enforce data protection policies (DLP, encryption, etc.)

• Detect risky behavior and misconfigurations

• Ensure compliance with regulations like GDPR, HIPAA, PCI-DSS

They support both sanctioned apps (like Google Drive) and unsanctioned or unknown cloud services.

Why CASB Is Critical in 2025

• SaaS adoption is accelerating — and not always IT-approved

• Remote and hybrid work shifts access points beyond perimeter

• Data breaches via cloud misconfigurations are increasingly common

• Compliance auditors demand clear oversight of cloud usage

• Traditional firewalls and proxies can’t see inside encrypted cloud traffic

A CASB gives you control, context, and clarity over your cloud environment.

Core Capabilities of CASB

1. Cloud Discovery (Shadow IT Detection)

   • Monitors user traffic to detect unsanctioned apps

   • Helps IT teams assess risk and block unauthorized services

2. Data Security

   • Applies DLP policies to cloud uploads, sharing, downloads

   • Prevents data exfiltration or accidental leaks

3. Threat Protection

   • Detects malware uploads, phishing links, and compromised accounts

   • Uses behavior analytics and threat intelligence

4. Access Control

   • Enforces contextual access policies based on device, user role, location

   • Supports MFA, session control, and time-based access

5. Compliance Monitoring

   • Tracks user activity, permissions, and content classification

   • Generates audit reports for GDPR, HIPAA, ISO 27001, etc.

CASB Deployment Modes

Each mode has trade-offs between real-time enforcement, coverage, and scalability.

Top CASB Vendors in 2025

Use Cases for CASB

• Blocking uploads of sensitive files to personal cloud drives

• Detecting abnormal login attempts to SaaS apps from unusual geolocations

• Preventing downloads of classified data to unmanaged devices

• Enforcing read-only access from mobile phones or public Wi-Fi

• Identifying overly permissive sharing in Google Drive or Box

CASB vs SASE vs SWG vs Zero Trust

CASB often works alongside SASE and Zero Trust architectures.

Best Practices for CASB Deployment

1. Start with discovery

   • Understand what cloud services your users actually use

2. Define acceptable use policies

   • Categorize apps (sanctioned, tolerated, unsanctioned)

3. Apply data-centric policies

   • Enforce DLP, encryption, and collaboration controls

4. Train users, don’t just block

   • Provide security alerts, tips, and alternatives

5. Monitor continuously

   • Cloud usage evolves — so should your policies