CASB: Cloud Access Security Broker
Cloud Access Security Broker (CASB) is a security solution that acts as an intermediary between users and cloud applications, providing visibility, control and data protection across SaaS, IaaS and PaaS environments. With the explosion in the use of cloud applications such as Microsoft 365, Google Workspace, Salesforce, AWS and hundreds of other tools, organizations have lost visibility and control over corporate data that now resides outside the traditional perimeter. CASB solves this problem by offering four fundamental pillars: Visibility (shadow IT discovery and cloud application inventory), Compliance (enforcement of regulatory policies and industry standards), Data Security (prevention of sensitive data leakage through cloud-native DLP) and Threat Protection (detection of threats, behavioral anomalies and malware in cloud services). The solution can operate in different deployment modes: inline (reverse proxy), API-based (direct integration with cloud providers) or log-based (analysis of access logs). Modern CASBs also implement granular context-based access controls (user, device, location, application), encryption for data at rest and in transit, tokenization to protect sensitive information, and integration with SIEM, EDR and IAM systems to create a unified and orchestrated security ecosystem.
Shadow IT Discovery and Cloud Visibility
One of the greatest corporate security challenges is the unauthorized use of cloud applications (shadow IT). Employees adopt SaaS tools without IT or security approval, creating dangerous blind spots. CASB offers cloud discovery through multiple methods: analysis of proxy and firewall logs, DNS query monitoring, integration with network traffic analysis and API connectors with identity providers. The result is a complete cloud app catalog, showing all applications in use, volume of data transferred, number of active users and the risk score of each app. Automatic risk assessment evaluates applications based on criteria such as security certifications (SOC 2, ISO 27001), privacy policy, breach history, data center location and GDPR compliance. The executive dashboard provides instant visibility into how many cloud applications are in use (often hundreds or thousands), which ones store sensitive data and which present security risks. App sanctioning allows security teams to classify applications as approved, unapproved or monitored, applying different policies to each category.
Data Loss Prevention (DLP) in the Cloud
CASB implements native DLP for the cloud, protecting sensitive data across SaaS applications. Content inspection examines uploads, downloads and shares in real time, using pattern matching, regular expressions and machine learning to identify: credit card numbers, national ID numbers, medical information (PHI), intellectual property, source code, contracts and other confidential data. Policy enforcement can block uploads of sensitive files, quarantine suspicious documents, apply automatic encryption, remove public sharing permissions or require additional MFA. Contextual controls enable granular policies: a financial document may be accessible from the office but blocked from unmanaged personal devices or unauthorized geographic locations. Data classification integrates with corporate systems, respecting confidentiality labels (Public, Internal, Confidential, Restricted). Remediation actions include encryption (using enterprise key management), tokenization (replacing real data with tokens), redaction (hiding sensitive portions of documents) and alerts for security teams and data owners. Integration with on-premises DLP ensures consistent policies inside and outside the corporate perimeter.
Threat Protection and Anomaly Detection
Modern CASBs implement advanced threat protection specific to cloud environments. Behavioral analytics uses machine learning to baseline normal user behavior and detect anomalies such as: login from an impossible location (impossible travel), massive data downloads (data exfiltration), excessive document sharing, creation of multiple service accounts or changes to critical configurations. Malware detection scans files in cloud storage using multi-engine antivirus, sandboxing and threat intelligence feeds. Account compromise detection identifies compromised credentials through abnormal login patterns, use of known malicious IPs or behavior inconsistent with the user's profile. Insider threat detection monitors the actions of privileged users, alerting on access outside business hours, data exfiltration prior to offboarding or violations of chinese wall policies. Integration with threat intelligence correlates cloud activities with global indicators of compromise (IoCs), identifying communication with C2 servers or use of applications associated with threat actors. Automated response can block users, revoke sessions, force password reset or escalate to the security operations center (SOC).
Compliance and Governance in Multi-Cloud
CASB is essential for maintaining regulatory compliance in cloud environments. Compliance monitoring continuously verifies whether cloud applications meet the requirements of GDPR, LGPD, HIPAA, PCI-DSS, SOX and other frameworks. For example, for GDPR: validating that data of European citizens is not stored in data centers outside the EU without legal safeguards, ensuring the right to be forgotten through data retention policies, auditing data processing activities and implementing privacy by design. For PCI-DSS: ensuring that card data is not stored in non-compliant applications, implementing encryption in transit and at rest, and maintaining audit trails of all access to CHD (cardholder data). Audit reporting generates automatic reports for audits, including access logs, data movement, policy violations and remediation actions. Data residency enforcement ensures data remains within specific geographies in accordance with regulatory or contractual requirements. Configuration auditing monitors cloud application settings (such as public S3 buckets, excessive permissions, weak encryption) and alerts on deviations from security baselines.
Deployment Modes and Architecture
CASBs can be implemented in different architectures according to needs: Inline/Proxy mode acts as a reverse proxy, intercepting all traffic between users and cloud apps in real time, enabling inline blocking and encryption. Advantage: real-time control. Disadvantage: additional latency and single point of failure. API mode connects directly to the APIs of cloud providers (Office 365, Google Workspace, Salesforce), enabling: data inventory, retroactive DLP on already stored files, remediation of insecure configurations and activity auditing. Advantage: no performance impact. Disadvantage: works only with apps that offer APIs. Log-based mode analyzes access logs generated by cloud apps, offering visibility and analytics without touching real traffic. Hybrid deployment combines inline for critical applications (real-time blocking) and API for broad coverage of the entire cloud ecosystem. Multi-tenancy support allows managing different policies for subsidiaries, departments or customers in MSP scenarios. High availability and scalability are critical so as not to become a bottleneck.
Integration with the Security Ecosystem
CASB does not operate in isolation but integrates with: Identity and Access Management (IAM) for enforcing policies based on user, group and role; Single Sign-On (SSO) for unified authentication; Multi-Factor Authentication (MFA) for step-up authentication on sensitive access; SIEM for correlating cloud events with on-premises security incidents; Endpoint Detection and Response (EDR) for access decisions based on device health and posture; Secure Web Gateway (SWG) for consistent web filtering and threat protection policies; Zero Trust Network Access (ZTNA) to implement never trust, always verify in cloud access; Cloud Security Posture Management (CSPM) for IaaS governance; Data Classification tools for automatic document labeling. This integration enables risk-based access control, where decisions to allow/block/step-up authentication are based on complete context: identity + device + location + application + data sensitivity + threat intelligence.
Use Cases and Implementation
Practical CASB use cases: (1) Control shadow IT: discover all cloud applications, assess risks and block unapproved apps while sanctioning secure alternatives; (2) Protect data in Office 365/Google Workspace: implement DLP to prevent external sharing of confidential documents; (3) Compliance with GDPR/LGPD: ensure that PII does not leave permitted geographies and maintain an audit trail of data processing; (4) Detect account takeover: identify suspicious logins and force MFA or block the session; (5) Secure BYOD: allow access to cloud apps from personal devices with restrictions (no download, view only); (6) Contractor access: grant limited access to third parties with enhanced monitoring. For a successful implementation: (1) start with discovery mode to map the cloud app landscape without blocking; (2) define policies based on risk and compliance requirements; (3) pilot with a small group before general rollout; (4) train users on approved apps and exception processes; (5) integrate with IAM/SSO for a transparent user experience; (6) monitor dashboards and adjust policies based on false positives/negatives; (7) conduct security awareness on the risks of shadow IT.