Why Microsoft 365 DLP Demands More Than Purview

Microsoft Purview handles sensitivity labels and pattern-based DLP rules. For checkbox compliance, that's sufficient. For preventing actual data loss in modern Microsoft 365 environments, it's not.

Your employees share PHI, PII, PCI or secrets and credentials in Teams screenshots that Purview's OCR misses. They download customer lists from SharePoint and sync them to personal OneDrive accounts you can't see. They paste financial projections from Exchange emails into ChatGPT. They convert proprietary spreadsheets to PDFs and email them to personal Gmail.

Purview sees some of this. It misses most of it. And even when it catches violations, you get alerts without the data lineage needed to understand what actually happened or prevent it from happening again.

Nightfall closes these gaps with AI-powered detection, complete data lineage across Microsoft 365 and endpoints, and forensic capabilities that reduce investigation time from days to minutes. Not by replacing Purview - by extending it with the advanced protection modern security teams actually need.

Scenario 1: The Teams Screenshot That Purview Can't See

What happens: Your healthcare operations manager receives a Slack message with patient appointment data. They need to share it with the scheduling team in Microsoft Teams. Rather than export and upload a file (which might trigger Purview), they take a screenshot and paste it directly into the Teams channel.

The image contains: patient names, dates of birth, medical record numbers, appointment times. Purview's pattern matching doesn't fire because it's an image, not text. If your organization configured Purview's premium OCR scanning, it might catch this - but at $0.10 per image with a 5-minute processing delay that happens post-violation, and only if you've purchased E5 compliance licenses.

Where Purview fails:

• No real-time OCR on images shared in Teams
• Pattern matching only works on text content
• Premium OCR requires expensive E5 licensing and processes after data is already shared
• No computer vision models to understand PHI, PCI, PII, secrets or credentials context in screenshots

How Nightfall prevents it: Pre-trained computer vision models scan every image shared in Teams in real-time. The screenshot contains PHI - medical record numbers combined with patient identifiers. Nightfall detects it with 95% precision and prompts the user to redact patient identifiers or share the data through a secure channel.

The entire detection happens in seconds. No per-image fees. No E5 licensing requirements..

Scenario 2: The SharePoint Download Purview Loses Track Of

What happens: Your departing sales director downloads the customer pipeline spreadsheet from SharePoint - 200 accounts with contact names, deal sizes, competitive intelligence, revenue projections. Purview logs the download. File access recorded.

Then they open the file on their MacBook, save it as a CSV with a generic filename ("data_export_2025.csv"), and upload it to their personal Dropbox via the browser. They email the Dropbox link along with sensitive content to their personal Gmail from their iPhone Outlook app.

Purview sees: SharePoint file download (alert generated). But it has no visibility into what happened after that download. Your SIEM shows browser activity to dropbox.com. Your endpoint logs show file operations. These are disconnected events with no context linking them together.

Where Purview fails:

• No visibility beyond the Microsoft 365 boundary
• Cannot track data after download to endpoint
• No detection of browser-based uploads to external services
• No data lineage showing the file's journey from SharePoint to endpoint to Dropbox to an email from their corporate account on their iPhone

How Nightfall prevents it: Complete data lineage from source to attempted destination. When the file is downloaded from SharePoint, Nightfall's endpoint agent detects and keeps a track of file movement. (Source: SharePoint, Classification: Financial - Confidential, Contains: Customer data + Revenue projections).

When the employee attempts to upload the renamed file via browser to Dropbox, Nightfall's endpoint agents and browser plugin intercepts before transmission. The system recognizes this is the SharePoint file that was downloaded 6 minutes ago, sees the destination is a personal cloud storage account, and blocks the upload immediately.

The data lineage shows you: User downloaded from SharePoint at 2:34 PM, Renamed file and attempted upload to personal Dropbox at 2:40 PM which was blocked.

You don't get three disconnected alerts. You get one complete story with the context needed for an intelligent response.

Scenario 3: The Outbound Email That Should Never Leave

What happens: Your finance team member forwards Q4 board materials to an external auditor. The email contains three attachments: a PowerPoint with revenue projections, an Excel spreadsheet with customer acquisition costs by segment, and a PDF showing competitive win rates. The recipient email address is external-auditor@temporaryemail.com - a disposable email service that will forward to unknown recipients.

The attachments contain: unreleased financial data, strategic customer information, proprietary competitive intelligence. Purview's rules flag "financial data to external recipient" but the email has already been delivered. By the time your security team investigates, the temporary email address has forwarded the content to three additional domains.

Where Purview fails:

• Post-delivery detection 
• No real-time classification of attachment content across multiple file types
• Cannot automatically encrypt based on content and recipient domain combination
• No quarantine-and-review workflow for sensitive outbound emails
• Limited remediation options after emails are already delivered

How Nightfall prevents it: Inline email scanning via Exchange Online connectors intercepts every outbound message before delivery. Pre-trained ML models analyze all three attachments in real-time: the PowerPoint contains financial projections (PCI + proprietary), the Excel file has customer acquisition data (PII + confidential), the PDF shows competitive intelligence (proprietary strategic content).

Recipient domain analysis: temporaryemail.com is flagged as high-risk disposable email service. Content and the destination is used to identify the critical violation. Nightfall takes immediate action:

• Block delivery entirely and notify sender with specific violation details
• Quarantine email in Exchange admin center for security team review before release
• Auto-encrypt using Nightfall’s encryption capabilities based on sensitivity and recipient domain rules

The employee receives instant coaching: "This email contains unreleased financial data and competitive intelligence being sent to a temporary email service. The email is blocked. Remove sensitive attachments and resend."

Real-time protection beyond email:

The same AI-powered detection works across all Microsoft 365 apps:

Teams: Scan messages and file uploads in real-time across channels, group chats, and 1:1 conversations. Allow employees to submit business justification for legitimate sharing of sensitive content.

OneDrive/SharePoint: Monitor file uploads and permission changes continuously. Detect when a document containing PHI gets shared via "anyone with the link" and automatically convert to private sharing or revoke external access. Apply delayed restrictions: allow 7-day collaboration period, then automatically change public links to owner-only.

Flexible remediation timing: Schedule delayed actions for files currently in use - wait 14 days for deal closure, then automatically revoke external partner access. Maintain business velocity without sacrificing security.

Automated incident response: REST APIs and webhooks integrate with your existing workflows:

• Send critical violations to Security team's Slack channel with one-click remediation options
• Create PagerDuty alerts for high-severity policy violations requiring immediate response
• Post summaries to Microsoft Teams with violation trends and suggested policy adjustments
• Email security analysts with detailed forensic data when sensitive files are downloaded to endpoints then uploaded to unauthorized services
• Trigger SOAR playbooks in Splunk/Sentinel for automated enrichment and containment

Configure custom webhooks to any system: ServiceNow for ticketing, Jira for case management, your internal compliance dashboard for executive reporting.

Scenario 4: The Copilot Prompt That Exposes Your Competitive Intelligence

What happens: Your product marketing manager is preparing a competitive analysis presentation. They've compiled proprietary research on competitor pricing, feature comparisons, and your go-to-market strategy in a Word document stored in SharePoint. To summarize it quickly, they open Microsoft Copilot in Edge, copy the entire document (23 pages), and paste it into a prompt: "Create an executive summary of our competitive positioning."

Microsoft Copilot processes the request. Your competitive intelligence - pricing strategies, planned features, target customer segments, weaknesses in competitor products - is now in Microsoft's LLM infrastructure. Purview has no visibility into Copilot prompts. Your CASB doesn't see clipboard operations. Your endpoint DLP logged copy activity but couldn't inspect or block the paste into a browser.

Where Purview fails:

• No visibility into Microsoft Copilot prompts or any other AI tool usage
• No monitoring of clipboard operations between Microsoft 365 apps and AI services
• Cannot detect when proprietary documents are being shared with external AI providers
• No content classification of prompt data (can't distinguish customer data from public information)

How Nightfall prevents it: AI-native interception monitors clipboard paste operations into all AI tools - Microsoft Copilot, ChatGPT, Claude, Gemini, Perplexity, and more. When the employee attempts to paste the 23-page competitive analysis, Nightfall scans the clipboard content in real-time before it reaches Copilot.

Pre-trained LLM models classify the document: Contains proprietary competitive intelligence + pricing strategy + product roadmap details equals High-sensitivity corporate IP.

Nightfall’s endpoint agent and browser plugin blocks the paste operation and provides immediate coaching: "This content contains proprietary competitive intelligence. AI services retain data that could be exposed through training or shared context. This activity is blocked and you can provide business justification for review”

Beyond Microsoft 365: Unified Protection Where Your Data Actually Lives

Purview stops at the Microsoft 365 boundary. Your data doesn't.

AI-native detection across your entire stack:

Nightfall's pre-trained ML models - 100+ detectors for credentials, PCI, PHI, PII plus 22 document classifiers - work identically across:

• Microsoft 365: Exchange, Teams, OneDrive, SharePoint, Google Workspace: Gmail, Google Drive, Collaboration platforms: Slack (messages + files), Atlassian (Jira, Confluence), Notion, Zendesk, Development tools: GitHub (commits, pull requests, issues), Business applications: Salesforce (records, attachments, Chatter)
• AI applications: ChatGPT, Claude, Gemini, Copilot, Perplexity, Deepseek - any AI tool accessed via browser or desktop app
• Endpoints: macOS, Windows devices covering browser uploads, cloud sync, USB, print, clipboard, git command line monitoring and more

Three products, one unified platform:

Data Detection & Response: Real-time scanning of data in motion across 10+ SaaS apps. Detects sensitive data as it's shared via email, messaging apps, CRM, cloud storage and productivity apps. Automatically block, encrypt, redact, or coach users before violations occur.

Data Exfiltration Prevention: Complete visibility across SaaS, endpoints and browsers, Shadow AI apps across all exfiltration vectors. Track downloads from SharePoint that get uploaded to personal Dropbox via browser. Monitor clipboard operations from Salesforce pasted into AI tools. Stop data leaving your environment across all egress vectors: browser uploads, cloud file sync, USB transfers, print operations, desktop apps and more.

Data Discovery & Classification: At-rest scanning across years of historical data. Identify sensitive content in OneDrive documents, files shared with departed employees still holding access. Bulk remediation: revoke access from 1,000+ stale permissions, delete documents with regulated data to avoid exposure, and automate remediation at scale.

Shadow AI governance without blocking innovation:

Nightfall is the first DLP platform that protects AI tool usage without forcing you to choose between security and productivity. Monitor prompts and file uploads to any AI application. Detect when employees paste proprietary code into ChatGPT or upload financial models to Claude. Block high-risk transfers automatically or sanitize content while allowing general AI usage.

Coverage extends beyond corporate-sanctioned AI (Microsoft Copilot) to Shadow AI: personal ChatGPT accounts, Perplexity on mobile browsers, Claude accessed via Arc, Deepseek, Gemini, any LLM service your employees discover.

Deployment That Matches Enterprise Reality

API-first architecture:

• Microsoft 365, Google Workspace, Slack, Salesforce, GitHub: Native API integration with OAuth 2.0
• Exchange Online: Inline connectors for real-time email scanning with zero latency impact
• Zero network changes, no proxies

Lightweight endpoints:

• macOS/Windows agents: <50MB memory footprint, <3% CPU usage
• Deploy via Microsoft Intune, Jamf, Kandji, or other MDM tools
• Silent installation, automatic updates, tamper protection

Browser coverage:

• Chrome, Edge, Firefox, Safari, Arc, Brave via MDM-managed extensions
• Operates inside encrypted HTTPS sessions (no SSL/TLS inspection needed)
• User-transparent until policy violation occurs

Pre-trained, not configured:

• 95% precision out-of-the-box without tuning
• 100+ ML detectors for credentials, PCI, PHI, PII. 22 document classifiers for business content. Image OCR and support for 150+ file types. 
• No regex rules to maintain, no data dictionaries to update
• Custom detectors train on natural language prompts + sample data

Production-ready in days:

• Week 1: Proof-of-value (scan sample Microsoft 365 data, demonstrate findings)
• Week 2-3: Full deployment (all SaaS apps, endpoints, browsers protected)
• Week 4: Optimize policies based on real violation patterns, fine-tune custom detectors

Organizations deploying Purview alone typically spend 3-6 months configuring rules, tuning regex patterns, and managing false positives. Nightfall's AI-native approach eliminates configuration complexity - protection starts the moment APIs connect.

Ready to learn more Nightfall’s comprehensive DLP for Microsoft 365? Schedule a demo today.