When shifting to the cloud, organizations need to ensure that cloud applications can be accessed only by authorized users. As your network perimeter changes, you need to implement security policies that adapt to the ever-evolving threat landscape. This article will explain what a cloud access security broker (CASB) is, the benefits of implementing one, and some security use cases for each mode of deployment.

What is a CASB?

A CASB is a security solution that sits between an organization's on-premises or remote infrastructure and its cloud applications, acting as an intermediary to monitor the traffic between them. These solutions are deployed using either proxies or APIs to identify if a connection to a cloud service is authorized or not. They provide an additional layer of security, enabling control over information shared across public and enterprise cloud apps.

Why should organizations use CASBs?

With organizations moving to the cloud and allowing employees to work from anywhere, the network perimeter is no more. Therefore, security teams need to adopt new ways of thinking about cybersecurity to secure their cloud infrastructure. CASBs can fill the security holes in the cloud, allowing security professionals to plan strategies, oversee threats, and gain complete visibility into sanctioned and unsanctioned cloud use.

Benefits of a CASB in an organization

  • Secures data from unauthorized access and cyberthreats
  • Monitors user behavior and responds immediately to any threats
  • Detects the presence and use of unmanaged devices and unauthorized applications in the network
  • Allows organizations to monitor user activity and reports if any anomalous activity is detected
  • Generates reports for compliance auditing purposes

CASB deployment modes and use cases

Organizations looking to implement CASBs in their networks should know that there are two deployment modes: proxy-based and API-based. Each deployment mode has its advantages and disadvantages. Therefore, companies need to understand the important use cases associated with each and make decisions based on their specific needs.

Proxy-based CASBs

The first generation of CASBs uses proxies to monitor access between known users and cloud applications. Traffic is rerouted through a proxy, allowing IT teams to add encryption security controls and monitor access attempts, logins, and usage. Proxy-based CASBs act as intermediaries between user devices and the cloud applications that the devices are attempting to access. Proxy-based CASBs are further divided into forward and reverse proxy modes.

Forward proxy use cases

Implementing granular access and activity controls

The CASB forward proxy can be integrated with the network firewall to monitor and enforce controls at the user activity level. For example, you can define a CASB policy to prevent users from accessing a specific application or uploading documents to certain websites.

Detecting shadow IT in your network

Every access request is sent through the CASB forward proxy, providing real-time information on what is happening to the data in transit. Therefore, forward proxies can detect whether a user is trying to access a sanctioned application or an unsanctioned one by using the web traffic logs. Learn about shadow IT.

Reverse proxy use cases

Enforcing access controls based on user behavior

CASBs can monitor user and entity behavior details, such as role, location, and time, to determine access levels and alert admins if anything malicious is detected. The CASB reverse proxy can be integrated with identity management applications to permit or restrict access to specific applications, files, and functions.

Preventing data loss from specific applications

Malicious insiders or external attackers can sometimes access sensitive data uploaded to internal applications. You can integrate a CASB with a DLP solution to apply granular access policies and prevent data exfiltration.

Encrypting corporate data residing in the cloud

CASBs can be integrated with key management services to encrypt certain types of data transferred to cloud services, such as email addresses and credit card numbers.

Controlling access to downloaded data

CASBs can be used to prevent the unauthorized export of critical data from cloud applications to unmanaged devices. This is done by integrating CASBs with endpoint agents and identity management solutions to detect if a download request is from a managed or unmanaged device and to restrict access to the data.

Auditing user activity in cloud applications

Placed closer to the cloud applications, the CASB reverse proxy integrates with identity providers to track user and admin activity inside cloud services. This lets security teams investigate the logs generated by the CASB tool and view the security incidents originating from the cloud services.

API-based CASBs

Alternatively, CASBs can use APIs to access and monitor data stored in the cloud. Because they use the cloud provider's built-in APIs, they allow IT professionals to customize access rules, automate incident responses, and gain deeper insights into activities performed in the cloud.

API use cases

Detecting malware in cloud services

API-based CASBs provide granular visibility into files stored in cloud services. This enables IT admins to detect and remove malware residing deep within. They can also integrate with malware detection solutions to strengthen malware diagnoses.

Enforcing data transfer policies across multiple cloud services

Employees may sometimes share sensitive corporate data with their personal email address or use two or more cloud apps to make their work easier. This comes with its own set of hazards. API-based CASBs can detect all the files shared with unapproved domains or anyone on the internet, then revoke permissions and shared links.

Auditing user access provisioning

API-based CASBs can detect whether the accounts that were granted permissions are still active or dormant. They can also detect the type of permission that was granted, such as admin or viewer.

Extending on-premises DLP policies to cover cloud data

API-based CASBs can be integrated with on-premises DLP solutions to audit files stored in cloud applications and perform necessary actions, such as deleting or encrypting files that were stored against DLP policies.

Do you need an extra tool in your security arsenal?

Today, the cybersecurity landscape is as complex as it gets, with varied categories of tools solving different security problems. Can a DLP tool become a CASB tool if it can encrypt data in the cloud? If a SIEM solution can collect endpoint logs, why do you need an EDR solution? The questions are endless. But it's safe to say that all these security solutions provide better visibility into and control over the incidents happening in your network when they integrate effectively with each other.

So, where does a CASB fit in your security posture?

As organizations continue to shift their operations to the cloud, their visibility into the data residing in their cloud apps tends to decrease. CASBs are here to fill in the gaps. CASBs can understand the context of data in transit or at rest, which a log collected from a SIEM solution or firewall lacks. They also allow existing security policies to extend to the cloud by integrating with and collecting log data from various on-premises tools:

  • DLP tools
  • Firewalls
  • Secure web gateways
  • Identity management tools
  • SIEM solutions

Even though CASBs provide visibility into external cloud usage, it is important to note that they are point tools. This means that the scope of coverage is limited and focused on cloud architecture. Therefore, organizations should never treat CASBs as the first line of defense for the cloud. You can get more value out of your security tools by becoming more cloud-aware with a CASB's rich cloud usage and behavior analytics.

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