Data loss is one of the most damaging -- and preventable -- cybersecurity risks facing Australian organisations. Whether it is a staff member accidentally emailing a spreadsheet containing customer tax file numbers to the wrong recipient, a departing employee downloading client files to a personal USB drive, or a misconfigured SharePoint site exposing sensitive documents to external users, the consequences are severe: regulatory penalties, reputational damage, and loss of customer trust.
The OAIC Notifiable Data Breaches Report (July-December 2024) recorded 527 breach notifications in a single six-month period. Human error accounted for 30% of all breaches, with email-related incidents being the single largest category. For organisations handling sensitive Australian data -- tax file numbers, Medicare numbers, financial records, health information -- the risk is not hypothetical.
Microsoft Purview Data Loss Prevention (DLP) provides automated, policy-driven protection that identifies, monitors, and protects sensitive data across Microsoft 365, endpoints, and cloud applications. It is the most effective tool available for preventing accidental and intentional data leakage in Microsoft-centric environments.
Key Takeaway
DLP is not about blocking employees from doing their jobs. It is about creating intelligent guardrails that prevent mistakes while allowing legitimate business activities to flow freely. Well-configured DLP policies are invisible to compliant users and only intervene when sensitive data is at risk.
How Purview DLP Works
Microsoft Purview DLP operates across three layers:
- Content inspection -- Scans the content of emails, documents, chats, and files for sensitive information patterns (credit card numbers, TFNs, Medicare numbers, etc.)
- Context analysis -- Considers who is sending the data, where it is going, and what application is being used
- Policy enforcement -- Takes action based on configurable rules: block the action, warn the user, require justification, encrypt automatically, or notify compliance teams
DLP policies can be applied across Exchange Online (email), SharePoint Online and OneDrive for Business (files), Microsoft Teams (chat and channels), Windows and macOS endpoints (local file activities), and Power BI (report sharing).
Sensitive Information Types for Australian Data
Microsoft Purview includes built-in sensitive information types specifically designed for Australian data:
| Sensitive Information Type | Pattern Detected | Common Use Cases |
|---|---|---|
| Australia Tax File Number (TFN) | 9-digit number with specific checksum validation | HR records, payroll, financial services |
| Australia Medicare Number | 10-11 digit Medicare card number | Healthcare, insurance, aged care |
| Australia Bank Account Number | BSB + account number patterns | Payroll, accounts payable, financial services |
| Australia Driver's Licence Number | State-specific formats | Identity verification, onboarding |
| Australia Passport Number | Letter + 7 digits | Travel, immigration, identity verification |
| Australia Business Number (ABN) | 11-digit ABN with checksum | Procurement, vendor management |
In addition to these built-in types, Purview supports custom sensitive information types using regular expressions, keyword lists, and machine learning classifiers. This enables organisations to detect industry-specific data patterns such as patient record numbers, policy numbers, or matter IDs.
Key Takeaway
The most effective DLP implementations start with a clear data classification scheme. Before configuring policies, identify what sensitive data your organisation holds, where it lives, and how it flows between systems and people. Precision IT's data discovery assessments map this landscape before a single policy is written.
Deployment Phases
Precision IT recommends a phased approach to DLP deployment that minimises disruption while building comprehensive protection:
Phase 1: Discovery and Classification (Weeks 1-4)
Deploy Purview in audit-only mode to discover where sensitive data exists across your Microsoft 365 environment. Map data flows and identify the highest-risk scenarios.
Phase 2: Policy Design (Weeks 5-6)
Design DLP policies targeting the highest-risk scenarios first: external email containing TFNs, file sharing with sensitive health data, bulk download of client records. Configure policies in "warn" mode initially.
Phase 3: Controlled Rollout (Weeks 7-10)
Enable policies in warn mode for target groups, collecting feedback and refining rules. This ensures policies do not block legitimate business activities while catching genuine risks.
Phase 4: Enforcement (Weeks 11-12)
Move policies to enforcement mode with appropriate actions: block, encrypt, require justification, or notify compliance. Implement endpoint DLP for USB and local file protection.
Integration with Essential 8 and Privacy Act
DLP directly supports compliance with the Essential 8 framework (particularly Application Control and User Application Hardening) and the Privacy Act 1988 (APP 11 -- security of personal information). For APRA-regulated entities, DLP supports CPS 234 requirements for protecting information assets commensurate with their sensitivity.
How Precision IT Deploys Purview DLP
As a Microsoft Solutions Partner and ISO 27001 certified MSP, Precision IT delivers end-to-end Purview DLP implementations for Australian organisations. Our cybersecurity practice handles data discovery, policy design, phased deployment, and ongoing policy management as part of our managed services.
Concerned about data leakage in your organisation? Request a complimentary data protection assessment and we will identify where your sensitive data lives, how it flows, and where the gaps in your current protection are.