Introduction
It’s not always hackers who leak your data sometimes it’s your own employees.
- A well-meaning staff member sends a client list to the wrong email.
- A developer uploads source code to a public repository.
- A remote worker saves a confidential file to their personal drive.
Every day, sensitive data leaves organizations unintentionally and that’s where ISO 27001 Control 5.51: Data Leakage Prevention (DLP) steps in.
This control ensures that confidential information stays protected, no matter where it travels inside your network, in the cloud, or beyond.
Because cybersecurity isn’t just about keeping threats out it’s about keeping your data in.
What Is Data Leakage Prevention (DLP)?
Data Leakage Prevention (DLP) refers to the tools, policies, and procedures designed to detect and prevent unauthorized data sharing or transfer.
DLP ensures that sensitive data like financial records, customer information, and intellectual property cannot leave your organization’s boundaries without approval.
Whether it’s through email, file transfers, USB drives, or cloud syncs, DLP acts as your last line of defense against human error and insider threats.
Why ISO 27001 Control 5.51 Matters
Data leaks can lead to severe consequences from financial loss and regulatory fines to reputational damage and loss of trust.
Control 5.51, from ISO/IEC 27002:2022 Section 5.51, is both a Technical and Organizational control that’s preventive and detective in nature.
It protects Confidentiality, Integrity, and Availability through the cybersecurity principles of Protect and Detect.
Implementing this control helps organizations:
- ✅ Prevent accidental or unauthorized sharing of sensitive data
- ✅ Monitor data flow across email, cloud, and endpoints
- ✅ Comply with privacy laws like GDPR, PIPEDA, and CPPA
- ✅ Strengthen trust with customers, partners, and regulators
How to Implement Data Leakage Prevention
To effectively apply ISO 27001 Control 5.51, organizations should:
Identify Sensitive Data
Classify data based on its importance and confidentiality level.
Use automated tools to detect sensitive data types (e.g., credit card numbers, PHI, customer info).
Set Up Data Leakage Prevention Tools
Deploy DLP software such as Microsoft Purview, Azure Information Protection, or endpoint DLP solutions.
Define and Enforce Data Sharing Policies
Create clear rules for how data can be sent, shared, or copied.
Block or encrypt sensitive data leaving via email or USB.
Monitor and Alert on Suspicious Activity
Implement continuous monitoring for data leaving corporate networks.
Educate Employees
Conduct training on recognizing and preventing accidental data leaks.
Common Mistakes in DLP Implementation
- 🚫 Treating DLP as a one-time setup instead of a continuous process
- 🚫 Focusing only on email and ignoring cloud platforms or endpoints
- 🚫 Overblocking legitimate business activity, leading users to find “workarounds”
- 🚫 Failing to align DLP with data classification and labeling systems
A good DLP system should be smart, adaptive, and user-friendly, not just restrictive.
Canadian Cyber’s Take
At Canadian Cyber, we help organizations build DLP frameworks that protect data without disrupting productivity.
We integrate Microsoft Purview DLP, Azure Information Protection, and endpoint controls with your ISO 27001 Information Security Management System (ISMS) giving you full visibility into where data goes, who’s using it, and how it’s shared.
Our approach focuses on:
- 🔹 Automating protection policies
- 🔹 Enabling contextual risk detection
- 🔹 Aligning DLP with compliance and business goals
Because real cybersecurity isn’t about blocking it’s about enabling secure business.
Takeaway
Data leaks don’t just happen from external attacks they often come from inside your walls.
ISO 27001 Control 5.51 Data Leakage Prevention ensures your sensitive data is monitored, controlled, and protected, wherever it goes.
With the right tools and culture, you can make sure your information stays where it belongs safe and secure.
How Canadian Cyber Can Help
At Canadian Cyber, we provide:
Data Leakage Prevention (DLP) Implementation and Policy Design
Microsoft Purview and Azure DLP Configuration
ISO 27001 and Privacy Framework Consulting (PIPEDA, GDPR, CPPA)
Connect with Us:
📩 Contact us: info@canadiancyber.ca
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