Cloud and SaaS DLP: Preventing Data Exfiltration Through Google Drive, Slack, and SaaS Apps
Retool's new app builder is where AI-generated code ships safely
Building apps with AI is easy. Getting them to production safely is another story.
Traditional DLP focuses on endpoints and email — the channels where data moved a decade ago. Modern data exits through: a file uploaded to a personal Google Drive from a corporate account, source code pasted into a ChatGPT prompt, customer data attached to a Slack message sent to an external workspace, or an S3 bucket accidentally set to public by a developer. These channels share one characteristic: they are entirely in the cloud, and traditional network DLP appliances or endpoint agents have limited visibility into them.
Cloud DLP and CASB (Cloud Access Security Broker) controls address these channels. This guide covers the architecture options, the priority deployment sequence, and the specific controls that prevent the most common cloud data exfiltration scenarios.
CASB architecture modes: which one to deploy
A CASB provides visibility and control over cloud application usage. Three deployment modes exist, each with different coverage and implementation complexity.
Subscribe to unlock Remediation & Mitigation steps
Free subscribers unlock full IOC lists, Sigma detection rules, remediation steps, and every daily briefing.
Google Workspace DLP: native controls to deploy first
Google Workspace includes native DLP controls in its security settings. For organizations on Google Workspace Business or Enterprise, deploying these native controls costs nothing additional and is the first step before investing in a third-party CASB.
Subscribe to unlock Remediation & Mitigation steps
Free subscribers unlock full IOC lists, Sigma detection rules, remediation steps, and every daily briefing.
Briefings like this, every morning before 9am.
Threat intel, active CVEs, and campaign alerts, distilled for practitioners. 50,000+ subscribers. No noise.
Microsoft 365 Purview DLP: priority deployments
Microsoft 365 E3 and E5 include Microsoft Purview DLP policies that apply across Exchange email, SharePoint, OneDrive, and Teams. E5 additionally covers endpoint DLP (application-level file activity on Windows/Mac). Deploy in audit-first mode to understand impact before switching to blocking.
Subscribe to unlock Remediation & Mitigation steps
Free subscribers unlock full IOC lists, Sigma detection rules, remediation steps, and every daily briefing.
Data discovery: finding sensitive data before controlling it
Effective cloud DLP requires knowing where your sensitive data lives. Attempting to enforce DLP policies without data discovery leads to both over-blocking (policies matching non-sensitive files) and under-blocking (sensitive data in locations the policies do not cover).
Subscribe to unlock Remediation & Mitigation steps
Free subscribers unlock full IOC lists, Sigma detection rules, remediation steps, and every daily briefing.
The bottom line
Cloud DLP requires a different architecture than traditional endpoint or network DLP because data moves through cloud APIs, not network perimeters. Start with native controls: Google Workspace DLP rules and sharing restrictions, Microsoft Purview DLP policies in audit mode. Add API-mode CASB for deeper visibility and data-at-rest scanning. Progress to inline proxy CASB for real-time blocking when native controls' enforcement is insufficient for your risk tolerance. In all cases, data discovery before enforcement prevents the false positives and coverage gaps that cause DLP programs to fail in practice.
Frequently asked questions
What is the difference between CASB and cloud DLP?
Cloud DLP refers to controls that detect and prevent sensitive data from being transmitted or stored inappropriately in cloud environments — it is a function. CASB (Cloud Access Security Broker) is a technology category that provides cloud application visibility, access control, threat detection, and data protection — it is a product type that delivers cloud DLP functionality along with other capabilities (cloud app discovery, user activity monitoring, threat detection). Microsoft Purview DLP is cloud DLP delivered as a native platform capability. Netskope, Zscaler, and Palo Alto CASB are cloud DLP delivered by a third-party CASB product. The function is the same; the delivery mechanism differs.
How do we handle personal cloud storage accounts accessed from managed corporate devices?
Corporate policy should prohibit uploading corporate data to personal cloud storage (Google Drive personal, personal Dropbox). Enforcement options: URL filtering to block personal cloud storage domains entirely on managed devices (simple but often too restrictive — employees use personal cloud for legitimate personal purposes), CASB with tenant restriction controls (allow access to corporate-tenant Google/Microsoft accounts only, block personal account access from managed devices), and endpoint DLP rules that detect and block file transfers to browser-based personal cloud upload pages. Tenant restrictions are the most targeted: they allow employees to access their personal accounts on personal devices but prevent corporate data upload from managed devices.
How should we handle ChatGPT and AI tool data exposure?
Prohibiting all AI tool use is generally ineffective — employees will use personal devices. More effective approach: provide a sanctioned AI tool with corporate data controls (Microsoft Copilot with Purview integration, a self-hosted LLM) as the approved channel, reducing demand for external tools. For residual external tool use: deploy browser extension-based content inspection (Microsoft Purview endpoint DLP, Nightfall browser extension) that detects sensitive content pasted into AI interfaces. Clear policy communication that defines what categories of data are prohibited from AI tools is essential — employees often do not understand what constitutes sensitive data without explicit guidance.
Sources & references
Free resources
Critical CVE Reference Card 2025–2026
25 actively exploited vulnerabilities with CVSS scores, exploit status, and patch availability. Print it, pin it, share it with your SOC team.
Ransomware Incident Response Playbook
Step-by-step 24-hour IR checklist covering detection, containment, eradication, and recovery. Built for SOC teams, IR leads, and CISOs.
Get threat intel before your inbox does.
50,000+ security professionals read Decryption Digest for early warnings on zero-days, ransomware, and nation-state campaigns. Free, daily, no spam.
Unsubscribe anytime. We never sell your data.
Founder & Cybersecurity Evangelist, Decryption Digest
Cybersecurity professional with expertise in threat intelligence, vulnerability research, and enterprise security. Covers zero-days, ransomware, and nation-state operations for 50,000+ security professionals every morning.
Win a $2,495 Black Hat pass.
Full-access to Black Hat USA 2026 in Las Vegas. Subscribe free to enter.