Table of contents
- What is Cloud Access Security Broker (CASB)
- Shadow IT and the invisible risks
- Integration with existing environments and Secure Web Gateway (SWG)
- Real-time protection and threat response
- The main CASB distribution models
- Key features of CASB
- CASB and Microsoft 365: a use case
- The future of Cloud Access Security
The flexibility and scalability of cloud applications offer unparalleled advantages, but at the same time data security represents one of the main challenges for companies. The massive adoption of services such as Microsoft 365, Google Workspace and Salesforce has expanded the risk perimeter, making on-premise protection alone insufficient.
Cloud Access Security Broker CASB comes into play, an essential component of modern security architecture. This article explores what the cloud access security broker is, why it is essential for data protection, how it integrates with existing technologies, and what benefits it offers for enterprise security.
What is Cloud Access Security Broker (CASB)
The Cloud Access Security Broker , abbreviated CASB, is an intermediary between an organization’s users and cloud service providers. Its task is to monitor, control and enforce security policies between users and cloud applications, regardless of whether they are on-premise or in SaaS environments. A CASB access security broker can be implemented as an on-premise solution, as a cloud service, or in a hybrid mode.
CASB offers advanced capabilities ranging from data protection to information loss prevention (DLP), from anomalous behavior detection to identity management. It operates in real time, ensuring complete visibility into all cloud applications used, including unauthorized or unknown ones, a phenomenon known as shadow IT.
Shadow IT and the invisible risks
Shadow IT refers to the use of SaaS applications or devices that are not approved by corporate IT. This behavior, while often driven by operational needs and the urgency to achieve results, introduces serious data security risks. CASB cloud access security brokers help identify and block these applications, reducing the attack surface and bringing control back under the corporate security umbrella.
Example
An employee may use a free file sharing service without encryption to share a sensitive document. A CASB, integrated into a cloud access security solution, can block the file upload in real time, log the event, and notify the administrator.
Integration with existing environments and Secure Web Gateway (SWG)
One of the most appreciated features of cloud access security brokers is the ability to integrate with existing security infrastructures, such as firewalls, Secure Web Gateway (SWG), SIEM tools, IAM solutions and endpoint protection.
Example
In combination with an SWG , a CASB can guarantee a double level of security: the first level acts on outgoing web traffic, the second monitors the interaction with cloud applications. This synergy ensures granular control of activities and enforcement of policies even on complex environments such as Microsoft 365, where access and permission management can be particularly delicate.
Real-time protection and threat response
Modern cloud access security brokers (CASBs) operate in real time, offering advanced threat protection capabilities. Using machine learning algorithms, CASBs can detect anomalies in user behavior, such as access from an unusual country or an attempted mass download from a suspicious data center.
Example
A properly configured CASB can automatically block a compromised account that attempts to download large amounts of data from a corporate cloud app, preventing a security breach. Additionally, with built-in threat intelligence capabilities, the system can constantly update itself to protect against new threats.
The main CASB distribution models
When adopting a Cloud Access Security Broker CASB, one of the first strategic decisions to make is which deployment model is best suited to your IT infrastructure. There are three main ones: API-based, proxy-based, and hybrid. Each model addresses specific needs and has distinct advantages and limitations.
CASB API-based: post-event auditing for critical SaaS
API-based model is based on direct integration between the cloud access security broker and cloud services via Application Programming Interfaces (APIs) provided by the provider (e.g. Microsoft, Google or Salesforce). This approach allows the CASB to access data and logs directly within cloud applications, without intercepting real-time traffic.
Advantages:
- Rapid deployment
No network changes or proxy configuration required. - Deep visibility into content
API access allows you to inspect documents, metadata, and user activity. - Perfect for SaaS like Microsoft 365 and Google Workspace, where APIs are stable, documented and secure.
- Great for compliance , auditing, data protection and shadow IT detection.
Disadvantages:
- It is not real-time
Detection and policy enforcement occur after the event. - It depends on the quality of the provider’s APIs
Not all cloud services offer extensive or high-performance APIs. - It cannot block access to cloud resources at the time of the request: it can only correct or alert post-event.
Example:
An organization using Google Drive can set up an API-based CASB to automatically analyze documents uploaded by users, identify files with sensitive data, and apply data loss prevention policies (e.g., encryption or automatic file removal).
CASB Proxy-based: real-time inspection and enforcement
The proxy-based model routes traffic between the user and the cloud application through a CASB-controlled proxy, which can be a forward proxy (for managed users) or a reverse proxy (for external or unmanaged users). This model allows for real-time control, blocking or modifying requests before they reach the cloud service.
Advantages:
- Real-time protection
Block dangerous uploads/downloads, apply dynamic security policies. - Granular control
Can modify content, interfaces and behaviors live, based on user, device or location. - Ideal for managing real-time threats or BYOD device access.
Disadvantages:
- More complex to implement
Requires changes to network or DNS configuration. - This may cause compatibility issues with some SaaS applications, especially if they use dynamic or certificate pinning mechanisms.
- Increased latency in traffic, especially for large files.
Example:
A multinational company sets up a CASB forward proxy for all employees accessing cloud apps like Dropbox. If an employee tries to upload a file with sensitive source code from a company laptop, the CASB immediately blocks the operation and alerts the CISO.
CASB Hybrid: the flexibility of the best of both worlds
hybrid model combines the capabilities of API-based CASB with those of proxy-based CASB, offering the highest degree of flexibility, coverage and protection. This architecture allows you to leverage real-time control where needed and apply post-event actions where proxy traffic is not manageable.
Advantages:
- Comprehensive coverage
Protects managed users, unmanaged users, supported apps, and non-API-integratable apps. - It provides dynamic protection for all cloud applications, including complex scenarios such as mobile or external user access.
- It is scalable and adaptable to any hybrid or multicloud environment.
Disadvantages:
- Higher cost
Requires a complete CASB solution, with multiple components. - Increased management complexity
You need to define when to use one or the other mode. - This can lead to configuration overlaps and the need for careful orchestration.
Example:
A healthcare organization uses a hybrid CASB to protect sensitive data in Microsoft 365 documents by blocking access from non-corporate devices in real time and retrospectively reviewing all files shared via APIs for protected health information (PHI) .
How to choose the right model?
The choice between distribution models depends on several key factors:
- Type of cloud applications used (Microsoft 365, Dropbox, Zoom, SAP Cloud…).
- Level of risk and compliance required (GDPR, HIPAA, PCI-DSS…).
- Presence of BYOD devices or external access.
- Latency and user experience requirements.
- Available IT budget and resources.
In many cases, a hybrid approach is the most effective, especially for organizations operating in highly complex or regulated environments. However, for startups or SMBs, an API-based CASB is often a sustainable and effective first step toward more robust cloud access security.
Key features of CASB
A CASB access security broker offers several critical features:
- Data Loss Prevention (DLP) to prevent the leakage of confidential information.
- Access control to manage permissions and authentication to cloud apps.
- Encryption and tokenization of data in transit and at rest.
- Threat protection to detect malware and suspicious behavior.
- Compliance auditing to ensure compliance with regulations such as GDPR, HIPAA or ISO 27001.
Thanks to these features, a CASB offers a multi-layered defense that is essential for companies that operate in highly regulated industries or handle large volumes of sensitive data.
CASB and Microsoft 365: a use case
Many organizations have adopted Microsoft 365 as their primary platform for productivity and collaboration. However, heavy use of OneDrive, Teams, and SharePoint means the risk of data loss or exposure increases exponentially.
A cloud access security broker CASB , integrated with Microsoft 365, can:
- Block sharing of files containing sensitive data with external users.
- Monitor anomalous user behavior, such as access from unauthorized devices.
- Apply granular security policies based on group membership, device, or geolocation.
The future of Cloud Access Security
The evolution of threats, the growth of SaaS applications and the continuous digital transformation require a radical change in the management of IT security. In this scenario, the cloud access security broker represents a key component for corporate security, which allows to balance the openness towards the cloud with the necessary data protection.
With the advent of AI, security orchestration, and Zero Trust architectures, the role of the CASB will increasingly be that of an intelligent orchestrator, able to dynamically adapt to the context and emerging threats, ensuring that the cloud can be truly secure.
Conclusions
Cloud Access Security Broker CASB is one of the most advanced and effective tools for managing the risks associated with cloud adoption today. From shadow IT protection to real-time threat defense, cloud application management and regulatory compliance, a well-implemented CASB is a guarantee of data security and business continuity.
Questions and answers
- What is Cloud Access Security Broker (CASB)?
It is an intermediary between users and cloud services, which controls access and enforces security policies. - Why is it important to use a CASB?
To protect sensitive data in cloud applications, detect threats, and block the use of unauthorized apps. - Is CASB also useful with Microsoft 365?
Yes, it allows you to monitor and control access to OneDrive, Teams and SharePoint. - What is Shadow IT?
It is the use of IT software or services not authorized by the organization, often hidden from the IT department. - Does CASB work in real time?
Yes, especially in proxy models, it monitors and blocks risky activities in real time. - What is the difference between CASB and SWG?
SWG protects web traffic, while CASB focuses on cloud apps. - Do you need to install software on users’ devices?
Not always: many CASB solutions are based on APIs or deployed in the cloud. - Can a CASB help with GDPR compliance?
Yes, with auditing and DLP capabilities to prevent data breaches. - How does CASB handle new vulnerabilities?
Through continuous updates and integration with threat intelligence. - Is CASB only suitable for large companies?
No, even SMBs can benefit from it, especially if they use a lot of cloud apps.
