Data Loss Prevention (DLP) detects and prevents sensitive data from leaving your organisation—whether through email, file sharing, cloud uploads, or AI tools. It's policy-based protection that stops data leakage before it happens.
Quick answer: Data Loss Prevention (DLP) detects and prevents sensitive data from leaving your organisation—whether through email, file sharing, cloud uploads, or AI tools. It's policy-based protection that stops data leakage before it happens.
What DLP Does
DLP monitors data and enforces rules:
Detect: Identify sensitive data based on patterns, keywords, labels, or machine learning
- Credit card numbers
- National Insurance numbers
- Health records
- Source code
- Financial data
- Whatever you define as sensitive
- Email attachments
- Cloud storage uploads
- Website submissions
- Removable media
- Print jobs
- AI tool inputs
- Block the action
- Warn the user
- Require justification
- Encrypt automatically
- Alert administrators
- Log for audit
Where DLP Works
Email DLP Scans outgoing emails and attachments. Blocks or encrypts messages containing sensitive data. "You're about to send customer credit card details externally—are you sure?"
Endpoint DLP Monitors activity on devices. Controls copy/paste, USB drives, printing, screen capture. Stops data leaving the device itself.
Cloud DLP Protects data in cloud services—Microsoft 365, Google Workspace, cloud storage. Controls sharing, downloading, external access.
Network DLP Inspects network traffic for sensitive data. Catches data leaving through any network channel.
AI/Web DLP The newest frontier. Detects sensitive data being pasted into AI tools, web forms, or cloud applications.
Microsoft Purview DLP
For Microsoft 365 environments, Purview DLP is the native solution:
What it covers:
- Exchange Online (email)
- SharePoint and OneDrive
- Teams messages and files
- Endpoint (Windows devices)
- Power Platform
- Defender for Cloud Apps (third-party cloud)
- Pre-built templates for common regulations (GDPR, PCI, etc.)
- Custom sensitive information types
- Sensitivity label integration
- User notifications and coaching
- Detailed activity logging
- Incident management
- Basic DLP in Microsoft 365 Business Premium
- Full DLP requires E5 or compliance add-ons
- Endpoint DLP requires E5 or add-on
Building a DLP Programme
1. Know your sensitive data
What data matters? Customer PII, financial records, intellectual property, health data? You can't protect what you haven't defined.2. Know where it lives
Discovery tools identify where sensitive data exists—file shares, SharePoint, email, cloud apps. Start with visibility.3. Define policies
What should happen when sensitive data is detected? Block? Warn? Encrypt? Log? Different data types and scenarios need different responses.4. Start with monitoring
Don't block immediately. Monitor first to understand patterns and avoid disrupting legitimate work. Tune policies before enforcement.5. Educate users
DLP shouldn't be a "gotcha." Users need to understand what's protected and why. Policy tips teach in the moment.6. Enforce gradually
Move from monitor to warn to block as policies mature. Sudden enforcement creates chaos.Common Mistakes
Blocking too much too fast Aggressive DLP breaks workflows and makes enemies. Start soft, tighten over time.
Not involving the business Security can't define what's sensitive alone. Finance, HR, Legal, and the business know what matters.
Ignoring false positives High false positive rates mean people ignore warnings. Tune your policies.
Forgetting AI tools Traditional DLP didn't cover AI chat interfaces. Modern programmes must.
What We Implement
We deploy Microsoft Purview DLP as part of our security services:
- Sensitive information type configuration
- Policy development aligned with your business
- Phased rollout (monitor → warn → block)
- Integration with sensitivity labels
- AI tool protection
- Ongoing tuning and management
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