Cloud Access Security Broker (CASB)
What Is CASB?
A Cloud Access Security Broker (CASB) is a security technology that sits between users and cloud services to enforce security policies, provide visibility into cloud activity, and protect sensitive data stored in or moving through cloud applications. CASB solutions help organizations monitor cloud usage, detect risky behavior, prevent data loss, and enforce compliance policies across Software-as-a-Service (SaaS), Platform-as-a-Service (PaaS), and Infrastructure-as-a-Service (IaaS) environments.
Overview
The widespread adoption of cloud computing has reshaped how organizations operate, but it has also introduced new security challenges. As employees increasingly rely on SaaS applications, cloud storage platforms, and web-based collaboration tools, traditional security models built around network perimeters have become less effective.
Users now access cloud services from remote locations, unmanaged devices, and personal networks. This shift limits the visibility and control that traditional tools like firewalls can provide. While those tools are still effective for monitoring network traffic, they often cannot see what users are doing inside cloud applications.
CASB technologies emerged to close this gap. By acting as an intermediary between users and cloud services, CASB solutions provide a layer of control that evaluates user activity, application behavior, and data interactions before allowing or restricting access. This enables organizations to apply consistent security policies across cloud environments without relying solely on network-based defenses.
How CASB Works
CASB functions as a policy enforcement point between users and cloud services. It monitors how users interact with cloud applications and applies security rules based on factors such as identity, device posture, location, and behavior.
In practice, CASB platforms provide several key capabilities:
- Discovering cloud services in use across the organization
- Monitoring user activity within SaaS applications
- Enforcing access controls based on context and policy
- Detecting anomalous or risky behavior
- Protecting sensitive data through data loss prevention (DLP) controls
To achieve this, CASB solutions typically operate through a combination of methods:
- API integrations with cloud providers to analyze data and configurations
- Proxy-based inspection to control activity in real time
- Log analysis to identify trends and uncover shadow IT
This layered approach allows CASB platforms to provide both visibility and control across cloud environments.
Core CASB Capability Areas
CASB platforms are often defined by four core functional areas that describe how they secure cloud environments.
Visibility
CASB tools identify which cloud services are being used across an organization. This includes both approved applications and unsanctioned tools, helping security teams detect shadow IT and understand overall cloud usage.
Data Security
CASB solutions protect sensitive information stored in or moving through cloud platforms. This includes enforcing policies around data sharing, applying encryption, and using DLP controls to prevent unauthorized exposure.
Threat Protection
CASB platforms detect suspicious activity within cloud services, such as compromised accounts or abnormal user behavior. They can identify potential threats and help organizations respond to security incidents more quickly.
Compliance
CASB supports regulatory and internal governance requirements by monitoring how data is accessed, stored, and shared. This helps organizations enforce policies related to data protection and maintain compliance with industry standards.
Types of CASB
API-Based CASB
API-based CASB solutions connect directly to cloud platforms using provider APIs. This approach provides deep visibility into data stored within cloud services, including files, permissions, and user activity.
These solutions are commonly used to monitor sanctioned SaaS applications and perform tasks such as auditing configurations or scanning stored data for sensitive information.
Proxy-Based CASB
Proxy-based CASB solutions sit in the traffic path between users and cloud applications. This allows them to inspect activity in real time and enforce policies during active sessions.
With this approach, organizations can block risky actions such as unauthorized downloads, uploads, or data sharing before they occur.
Multi-Mode CASB
Multi-mode CASB solutions combine API integrations with proxy-based inspection. This provides both real-time control and deeper visibility into stored cloud data, offering a more comprehensive approach to cloud security.
Causes and Risks That Led to CASB Adoption
Several factors contributed to the rise of CASB as a critical component of cloud security.
The rapid expansion of SaaS applications has made it difficult for organizations to track which tools are in use. Employees often adopt new applications without IT approval, leading to shadow IT and increased risk.
At the same time, remote work and bring-your-own-device (BYOD) environments have expanded the number of access points to cloud services. Sensitive data is frequently stored and shared through cloud collaboration platforms, increasing the potential for accidental exposure or misuse.
Regulatory and compliance requirements have also played a role. Organizations must now demonstrate control over how data is accessed and shared, even when it resides in third-party cloud environments.
Traditional network security tools struggle to provide visibility into these scenarios, creating a need for solutions specifically designed to monitor and control cloud application activity.
Effects of CASB
The adoption of CASB technologies has led to several important improvements in how organizations manage cloud security.
Improved cloud visibility
Security teams gain a clearer understanding of which cloud services are being used and how employees interact with them. This visibility helps uncover shadow IT and reduces blind spots.
Stronger protection for sensitive data
CASB solutions help prevent data leaks by detecting and blocking risky transfers, such as uploading sensitive information to unauthorized applications.
More granular access control
Organizations can enforce policies that consider user identity, device status, and location. This allows for more precise control over who can access data and how it can be used.
Improved governance and compliance monitoring
CASB platforms support compliance efforts by monitoring data handling practices and enforcing policies aligned with regulatory requirements.
Reduced risk from shadow IT
By identifying unsanctioned applications and controlling access, CASB helps organizations reduce the risks associated with uncontrolled cloud usage.
Compare CASB to Other Security Tools
CASB vs Secure Web Gateway (SWG)
CASB focuses on monitoring and governing activity within cloud applications, while Secure Web Gateways (SWG) are designed to inspect and control general internet traffic.
SWGs are effective for enforcing web usage policies and blocking malicious websites, while CASB provides deeper visibility and control within SaaS platforms. Many modern security architectures combine both capabilities.
CASB vs Firewall
Firewalls monitor and filter network traffic entering or leaving a network based on predefined rules. They are designed to protect network boundaries and control access at the infrastructure level.
CASB technologies, in contrast, focus on cloud services and SaaS activity. Rather than filtering traffic based on IP addresses or ports, CASB solutions analyze user behavior and data interactions within cloud applications.
CASB vs Proxy
A proxy routes and inspects traffic between users and external services. While CASB platforms may use proxy techniques, they extend beyond simple traffic routing.
CASB solutions provide cloud-specific controls, including activity monitoring, data protection, and compliance enforcement, making them more specialized for cloud environments.
CASB vs Identity and Access Controls (SSO)
Identity systems such as Single Sign-On (SSO) manage authentication and provide users with access to applications.
CASB platforms operate after access is granted. They monitor how applications are used and enforce policies related to data access, sharing, and behavior within cloud environments.
These technologies often work together as part of a broader cloud security strategy.
By the Numbers
CASB and Cloud Security Statistics
106 SaaS applications per organization
Organizations now use an average of over 100 SaaS applications, illustrating how quickly cloud environments become difficult to manage without centralized visibility and control.
* Source: https://www.bettercloud.com/monitor/2025-state-of-saas-trends/
305 SaaS applications in the average enterprise
Large organizations manage hundreds of cloud applications, increasing the risk of misconfigurations, inconsistent policies, and unauthorized access.
* Source: https://www.cfodive.com/news/enterprise-software-bills-climb-amid-ai-pricing-volatility-zylo/810908/
$49 million in annual SaaS spending
Enterprises now invest heavily in cloud applications, making it critical to monitor how data is accessed, shared, and secured across these platforms.
* Source: https://www.highalpha.com/blog/navigating-saas-spending-in-2025-insights-from-zylos-saas-management-index
Examples of CASB
Real-World Examples
A company uses CASB to identify employees uploading sensitive documents to unsanctioned cloud storage services, helping prevent data leakage.
A security team enforces policies that prevent confidential files from being downloaded from corporate SaaS applications onto unmanaged devices.
A financial institution monitors cloud collaboration platforms to detect risky file sharing that could expose regulated data.
An enterprise security team uses CASB analytics to detect abnormal login patterns that may indicate compromised SaaS accounts.
Who Might Need CASB
Organizations heavily reliant on SaaS platforms often benefit from CASB solutions, particularly when managing large numbers of applications and users.
Businesses with distributed or remote workforces may use CASB to maintain visibility and control across different environments and devices.
Companies handling sensitive data, such as financial or healthcare information, use CASB to enforce stricter data protection policies.
Enterprises seeking greater insight into cloud usage and improved governance often adopt CASB as part of a broader security strategy.
Related Terms
- Secure Web Gateway (SWG)
- Secure Access Service Edge (SASE)
- Data Loss Prevention (DLP)
- Zero Trust Network Access (ZTNA)
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