What is a CASB? A Complete Guide to Cloud Access Security Brokers

In 2025, cloud and SaaS platforms have become the backbone of how we work. It’s convenient, efficient, and for many of us, it’s hard to remember how we ever operated without it—especially in a post-pandemic world where remote collaboration is the norm.

Organizations everywhere are embracing cloud services to drive flexibility, innovation, and operational efficiency. However, with the widespread adoption of cloud platforms comes an increase in security risks. Sensitive data is more vulnerable to unauthorized access, data breaches, and insider threats. Ensuring data security across multiple cloud environments has become a pressing concern for organizations of all sizes.

This is where a Cloud Access Security Broker (CASB) plays a critical role. A CASB acts as a vital security layer between cloud service users and cloud applications, providing visibility, control, and protection over data and user activities. It enables organizations to monitor cloud access, enforce security policies, and prevent data loss while mitigating risks and ensuring compliance with industry standards.

In this guide, we will explore everything you need to know about CASB’s from functionalities, features, deployments, use cases, integration considerations, and more. You'll gain an in-depth understanding of how CASBs work and how they can help your company enhance cloud access security.

What is a CASB?

A Cloud Access Security Broker (CASB) is a security solution that operates as an intermediary between users and cloud services, ensuring secure access, monitoring data traffic, and enforcing security policies. CASBs provide organizations with essential visibility and control over how data is accessed, shared, and stored across cloud platforms.

By acting as a security broker, CASBs enable enterprises to detect and manage unauthorized applications, protect against data loss, and safeguard sensitive information from both external and internal threats. 

A CASB monitors traffic and applies security measures such as data loss prevention (DLP), encryption, access controls, and threat protection to maintain a secure cloud environment.

There are various types of CASB deployments, including API-based and proxy-based models, each offering unique capabilities to meet organizational needs. 

Regardless of the deployment model, the core function of a CASB is to enhance cloud security, provide consistent policy enforcement, and ensure secure access to critical data and applications.

Why are CASB’s Important?

Implementing a CASB is vital for organizations looking to protect sensitive information, enhance cloud access security, and meet compliance requirements. Here's why CASBs are indispensable in modern cloud security strategies:

• Improved Data Security: CASBs protect sensitive data by monitoring and controlling access to information stored in cloud services. Through data loss prevention (DLP), encryption, and access controls, CASBs ensure that only authorized users can access, share, and store critical data. This helps prevent data breaches and safeguards intellectual property.

• Enhanced Visibility Across Cloud Services: One of the primary roles of a CASB is to provide deep visibility into user activities, data movements, and application usage across all connected cloud services. This visibility allows organizations to detect anomalies, identify potential security risks, and ensure that security policies are consistently enforced across the entire cloud environment.

• Compliance with Industry Standards: Regulatory compliance is a major concern for businesses handling sensitive information. CASBs assist organizations in adhering to frameworks such as GDPR, HIPAA, and SOC 2 by enforcing security policies, generating audit reports, and providing detailed insights into data usage. This capability helps organizations mitigate risk and avoid costly non-compliance penalties.

• Mitigation of Insider Threats: Insider threats remain a significant concern for organizations. CASBs help detect and mitigate these risks by monitoring user behavior, applying access control policies, and flagging suspicious activities. This proactive approach ensures that unauthorized access or malicious actions are identified and addressed promptly.

In essence, CASBs offer organizations a strategic approach to managing cloud security challenges. They empower security teams with the tools needed to monitor, control, and secure cloud environments, thereby reducing risk and enhancing overall data security.

Overview of CASB Functionality

CASBs serve as an essential security solution designed to secure cloud services by providing comprehensive visibility, control, and threat protection. Here's a closer look at how CASBs function and why their role is pivotal for modern organizations:

How Does a CASB Work? 

As we mentioned, CASBs work by monitoring and controlling the flow of data between users and cloud services. 

They inspect data in transit and at rest, enforce security policies, and apply security measures such as encryption, access control, and data loss prevention. 

CASBs can operate using API integrations or proxy models to ensure that data remains secure across various platforms.

Key Functionalities of CASBs:

• Visibility: CASBs provide complete visibility into user activity, data movement, and application usage across the cloud ecosystem. This ensures that organizations can detect shadow IT, monitor security incidents, and maintain control over sensitive data.

• Data Protection: Through features like DLP, encryption, and access control, CASBs safeguard sensitive information from unauthorized access, ensuring data security across multiple platforms.

• Threat Prevention: CASBs proactively detect and mitigate security threats, such as unauthorized data sharing or anomalous behavior that may indicate insider threats or external attacks.

By combining these functionalities, CASBs empower organizations to secure their cloud environments efficiently and effectively.

Key Features of a CASB:

To offer robust cloud access security, CASBs provide a range of advanced features:

• Data Loss Prevention (DLP): CASBs utilize DLP capabilities to identify, monitor, and protect sensitive data from unauthorized access and potential leaks. DLP policies help prevent data breaches by restricting the sharing of critical information outside of trusted networks.

• Shadow IT Discovery: Unapproved applications pose significant risks to data security. CASBs provide deep insights into shadow IT by discovering and monitoring unauthorized cloud services. This allows security teams to assess potential risks and enforce appropriate controls.

• Compliance Management: Maintaining regulatory compliance is critical for organizations. CASBs simplify this by enforcing compliance-based security policies, providing audit trails, and ensuring secure data management in alignment with frameworks like HIPAA, GDPR, and SOC 2.

• Threat Protection: CASBs offer robust threat protection by identifying suspicious behavior, detecting malware, and blocking malicious activity. This feature is essential for mitigating both insider and external threats to cloud services.

• Encryption and Tokenization: To further protect sensitive information, CASBs provide encryption and tokenization solutions that secure data at rest and in transit. These methods ensure that even if data is intercepted, it remains inaccessible without proper decryption keys.

By leveraging these features, organizations can enhance cloud security, improve risk management, and ensure the protection of sensitive data across their entire cloud infrastructure.

Types of CASB Deployments

There are two primary types of CASB deployments: API-based and Proxy-based. Each has unique characteristics and is suited to specific use cases.

API-Based CASB 

API-based CASBs integrate directly with cloud services using secure APIs. API stands for ‘Application Programming Interface’. APIs act as the language that allows different software applications to talk to one another.

An API-based approach offers real-time visibility and control without impacting network performance. API-based CASBs are particularly effective in securing SaaS applications and monitoring user activities. They provide efficient data analysis and can be seamlessly integrated into different cloud environments.

API based CASB’s are quicker when it comes to detection, but also when it comes to set-up time. Since an API is more fluid than traditional models, time to value using an API-based CASB can be a better return on investment for organizations looking to start up and scale up quickly.

There are two main architectures for API-based CASBs:

1. Pull-Based (Legacy Approach):

Older solutions operate on a pull-based model, scanning data at scheduled intervals—often every few hours. They detect changes (deltas) since the last scan, which can delay threat detection and create gaps in visibility.

2. Push-Based (Modern Approach):

Modern solutions, like DoControl, leverage a push-based, event-driven architecture. This enables real-time detection and remediation of risks as they occur, ensuring immediate response to security events without hindering business productivity.

Proxy-Based CASB 

Proxy-based CASBs function by redirecting user traffic through a security proxy, inspecting data in transit. They operate by intercepting traffic at the network layer, and inspecting all data streams. There are two types:

• Forward Proxy: Positioned between users and the cloud service, inspecting outbound traffic.
• Reverse Proxy: Positioned between the cloud service and the user, inspecting inbound traffic.

Proxy-based models offer detailed traffic inspection and stronger data protection but may introduce latency. 

Traditional proxy-based CASBs have a rigid approach to security; this is because there is a ‘middle man’ put in place to block actions–which often hurts business productivity and gives false positives. 

One more thing to note about proxy-based CASBs is that they often take a while to fully deploy and take time to see value. These systems are complex and require a few months (maybe years in some cases) to deliver results. Integrating these into environments requires careful consideration and configuration to ensure optimal performance.

Common CASB Use Cases

Securing SaaS Applications‍

CASBs ensure that SaaS applications are secure by monitoring data flows, enforcing security policies, and providing threat protection. 

For example, a CASB can detect if sensitive data, like customer financial information, is being shared externally through a SaaS tool and automatically block the transfer or alert administrators. 

Managing Shadow IT and Third Party Applications

Detecting and controlling unauthorized third-party applications is essential for security. CASBs identify shadow IT by monitoring cloud activity and flagging any unauthorized apps being used by employees. 

For instance, if an employee uses an unapproved file-sharing service to store work documents, the CASB can alert the security team and either block the app or guide the user to an approved, secure alternative.

Ensuring Data Compliance‍

CASBs automate compliance checks and provide detailed reports, making it easier for organizations to meet regulatory standards. 

For example, a CASB can monitor data storage and usage across cloud services, automatically flagging instances where sensitive data handling doesn't align with regulatory requirements. This helps organizations stay compliant without needing constant manual oversight.

Protecting Against Malware‍

CASBs offer advanced detection and prevention capabilities, helping to identify and block malware threats within cloud environments. 

For instance, if a user unknowingly uploads an infected file to a shared cloud drive, the CASB can scan the file, detect the malware, and quarantine it to prevent it from spreading across the network.

Challenges and Factors to Consider When Choosing a CASB Solution

Common Implementation Challenges

• Complex Integration: Integrating CASBs with diverse cloud environments can be challenging. Businesses must ensure that the solution supports all required platforms.
• Scalability: As organizations grow, ensuring the CASB can scale with increasing data volumes and users is critical.
• Policy Management: Configuring and maintaining consistent security policies across multiple cloud services can be complex.

Limitations in Coverage or Integration

• Limited API Support: Not all CASBs support every cloud service API, which can limit their effectiveness.
• Latency Concerns: Proxy-based CASBs may introduce latency in traffic flow, affecting user experience.
• Restricted Visibility: Without comprehensive integration, organizations might lack full visibility into shadow IT and unsanctioned applications.

DoControl: Designed for Modern Businesses

Choosing the right CASB solution is essential for securing cloud environments, protecting sensitive data, and ensuring compliance. API-based CASBs offer a seamless, scalable approach that aligns with modern cloud strategies.

DoControl offers an API-CASB designed for modern businesses. Unlike traditional proxy-based solutions, DoControl integrates directly with cloud service APIs, providing deeper visibility, real-time monitoring, and advanced threat protection. This approach simplifies integration, enhances performance, and ensures security without compromising user experience.

DoControl bridges the gap between SSPM and CASB. We redefined our identity over the last 12 months from being a next-gen CASB to now a cutting-edge SSPM. We do a lot more than traditional CASBs, and are continually finding our place in such a unique market.

Our positioning ensures that organizations benefit from comprehensive security, governance, and compliance capabilities. By offering automated controls, workflows, visibility, and remediation, DoControl empowers businesses and its partners to confidently protect their SaaS environments.

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