What Is a Cloud Access Security Broker (CASB)?

A Plain-English Guide to Securing Cloud Apps in Your Business

Executive Summary

A Cloud Access Security Broker (CASB) helps your business keep control of cloud-based apps like Microsoft 365, Google Workspace, Dropbox, and Salesforce. It sits between your users and the cloud, checking who’s accessing what, spotting risky behaviour, and keeping sensitive data from leaking out.

If your business uses cloud apps, CASB gives you the visibility and control traditional IT tools simply don’t.

Introduction

This blog is part of our Secure Service Edge (SSE) and Secure Access Service Edge (SASE) series, breaking down the key components of modern, cloud-first security.

New to the series? Start here:

 SSE vs. SASE: What’s the Difference, and What Does Your Business Need?

Now let’s zoom in on one essential piece of the puzzle: CASB, the cloud security layer your business probably needs (even if you’ve never heard of it before).

What Is a CASB?

A Cloud Access Security Broker is a service that helps you monitor, control, and secure how your users access and use cloud-based software.

It works by:

  • Sitting between your users and your cloud apps
  • Watching for risky behaviour or unauthorised activity
  • Enforcing security policies (like blocking downloads of sensitive data)

What Problems Does CASB Solve?

Many businesses have moved to the cloud but have lost some visibility and control along the way.

CASB helps with:

  • Shadow IT (when employees use unapproved apps or services without IT’s knowledge)
  • Data loss prevention
  • Compliance
  • Risk reduction

A Real-World Example

You’ve given your team access to Microsoft 365, and they’re working well in the cloud. But someone decides to back up files to their personal Dropbox account. Without CASB, that file is now:

  • Out of your control
  • Potentially in breach of your policies
  • Possibly exposing confidential client info

With CASB in place:

  • The upload is blocked or flagged
  • You’re alerted instantly
  • The data stays secure

Frequently Asked Questions

Do I need a CASB if I already use MFA and encryption?

Those are great first steps, but they don’t monitor user behaviour in real-time. CASB adds that extra layer of visibility and control.

Does CASB work with all cloud apps?

Most leading CASB tools integrate with Microsoft 365, Google Workspace, Dropbox, Box, Salesforce, and many more. It depends on the tool, but coverage is usually broad.

Can I stop staff using unapproved apps?

Yes. CASB can detect ‘shadow IT’, apps your IT team hasn’t approved, and block or report them.

Is this only useful for large enterprises?

Not at all. CASB is valuable for any business using cloud apps and managing sensitive data ,especially if you want to improve compliance and reduce risk.

Is CASB part of SASE or SSE?

Yes, CASB is a core component of SSE and therefore also included in SASE. It’s all about securing cloud app usage.

Next Steps

If your business relies on cloud apps to get things done, a CASB helps you keep things secure, compliant, and under control, without locking everything down.

Ready to add cloud app visibility to your business?
Just ask your Get Support Customer Success Manager or call our team on 01865 594000.