A security checkpoint residing either on-premises or in the cloud and positioned between cloud service users and cloud applications. It acts as a gatekeeper, allowing organizations to extend their security policies from their own infrastructure to the cloud. CASBs ensure that network traffic between on-premises devices and cloud providers complies with an organization’s security policies.
The Four Pillars of CASB
To provide comprehensive protection, a CASB solution is built upon four functional pillars:
- Visibility: The ability to detect all cloud services in use (including Shadow IT), identifying who is using them, from which department, and on what device.
- Compliance: Ensuring that cloud usage meets data privacy regulations (like GDPR, HIPAA, or PCI-DSS) and identifying whether cloud providers themselves meet industry standards.
- Data Security: Extending Data Loss Prevention (DLP) to the cloud. This includes the ability to identify, monitor, and stop the movement of sensitive data to or from cloud environments.
- Threat Protection: Preventing cloud-based threats such as malware and ransomware. This involves using User and Entity Behavior Analytics (UEBA) to detect anomalous behavior that might indicate a compromised account.
How It Works: Deployment Modes
CASBs function through different architectures depending on the organization’s needs:
- API-Based (Out-of-Band): The CASB connects directly to the cloud provider’s API. This provides deep visibility into data-at-rest within the cloud but cannot block threats in real-time before they reach the cloud.
- Forward Proxy: Positioned between the user and the cloud. It manages requests from managed devices to the cloud, making it ideal for enforcing policies on corporate-owned assets.
- Reverse Proxy: Positioned in front of the cloud application. It manages traffic from any device (including unmanaged/personal devices) to the cloud, which is essential for Bring Your Own Device (BYOD) security.
CASB vs. Traditional Firewall
| Feature | Next-Gen Firewall (NGFW) | CASB |
| Primary Focus | Defending the network perimeter | Defending data within cloud apps |
| Visibility | IP addresses and ports | Deep granular activity (e.g., Share, Delete, Download) |
| Shadow IT | Limited detection | High-fidelity discovery of thousands of SaaS apps |
| Device Scope | Primarily on-network devices | Both managed and unmanaged (BYOD) |
Key Benefits
- Shadow IT Discovery: Reveals “hidden” cloud usage where employees might be using unauthorized tools (like personal file-sharing sites) to handle corporate data.
- Granular Access Control: Instead of just allowing or blocking an app, a CASB can allow a user to view a document in the cloud but block them from downloading it to a personal device.
- Data Encryption: Provides the ability to encrypt sensitive content before it is even uploaded to the cloud service, ensuring the cloud provider cannot see the raw data.
