PUR511 – Audit Everything, Investigate Anything: The Role of Microsoft Purview Audit

Introduction

In every investigation , whether it’s a security breach, policy violation, or regulatory inquiry , one question always matters most:
“What exactly happened, and who did it?”

That’s where Microsoft Purview Audit steps in.
It gives your organization a forensic record of every user and admin activity across Microsoft 365.
From file downloads and label changes to Copilot interactions and mailbox access , Purview Audit provides the evidence trail that proves compliance and supports incident response.

Audit isn’t glamorous, but it’s one of the most powerful tools in your governance toolbox.

Why Auditing Matters

Without audit logs, investigations rely on guesswork.
With them, you can:

• Verify if sensitive data was accessed, modified, or shared.
• Reconstruct security incidents in sequence.
• Demonstrate compliance to regulators and auditors.
• Detect misuse of privileged or admin accounts.

In short, auditing turns activity into accountability.

Microsoft Purview Audit Tiers

Purview offers two audit levels:

Audit (Premium) adds deeper visibility, longer retention, and richer data for investigations , especially critical in regulated industries like finance or healthcare.

What Audit Captures

Audit records activities from virtually every Microsoft 365 workload:

• Microsoft Entra ID – sign-ins, group and role changes
• Exchange Online – mailbox access, message deletion, forwarding rule creation
• SharePoint / OneDrive – file views, edits, sharing events
• Teams – message edits, meeting joins, file shares
• Copilot / AI tools – prompt and interaction metadata
• DLP / Insider Risk – policy alerts and enforcement actions

Each log entry includes who performed the action, what they did, when it happened, and from where (IP address and device details).

How Purview Audit Works

Every activity performed in Microsoft 365 generates an event that’s stored in the Unified Audit Log.
Administrators or investigators can search these records using:

• Purview portal → Solutions → Audit
• PowerShell cmdlets (Search-UnifiedAuditLog)
• Office 365 Management Activity API for SIEM integration

Audit is on by default for most tenants , ensuring no gaps in visibility from day one.

Audit Retention and Storage

Retention policies can target specific services, users, or activity types.
When policies overlap, the longest retention period wins , ensuring no premature data loss.

Advanced Audit (Premium) Capabilities

Audit Premium introduces several investigation-grade features:

• Intelligent Insights: High-value event context (e.g., “Mail Item Accessed”).
• Extended Retention: Up to 10 years , crucial for legal holds and long-term compliance.
• Audit Search Graph API: Enables automation and advanced queries.
• Higher API Bandwidth: Faster export to SIEM or Power BI.
• Copilot Interaction Logging: Tracks prompts, responses, and resource references for AI governance.

These enhancements elevate Audit from compliance logging to true forensic analysis.

Real-World Example: Investigating a Data Leak

Scenario:
The compliance team notices sensitive financial data shared externally via email.

Steps using Purview Audit:

1. Search the Unified Audit Log for the user’s activity within the suspected timeframe.
2. Filter by “Send message” and “File shared externally.”
3. Review audit details: IP address, device name, message ID, and recipients.
4. Correlate with DLP alerts to verify the rule triggered correctly.
5. Export results to CSV for evidence and documentation.

In minutes, the organization confirms who sent the file, from which location, and which policy applied.

Auditing Microsoft Copilot and AI Interactions

As AI tools enter everyday workflows, Purview Audit keeps them governed.
It records Copilot activity metadata such as:

• Who interacted with Copilot
• When and from which service (e.g., Word, Outlook)
• Prompt context and associated data sources

You can’t view user prompts or generated text for privacy reasons, but you can trace when and how AI accessed corporate data , critical for proving responsible AI use.

Working with Audit Logs in PowerShell

Investigators often need deeper or automated searches.
Example command:

Search-UnifiedAuditLog -StartDate “10/01/2025” -EndDate “10/10/2025” `

-UserIds “user@contoso.com” -RecordType SharePointFileOperation `

-Operations FileAccessed -ResultSize 2000 | Export-Csv “C:\Audit\SharePointAccess.csv”

This exports every file access action by the user during the specified window.
Combine it with filters like ClientIP or Operation for pinpoint accuracy.

Integration with Other Security Tools

Purview Audit data feeds into:

• Microsoft Defender XDR – for cross-threat correlation.
• Microsoft Sentinel – for real-time alerting and visualization.
• eDiscovery (Premium) – for legal evidence linking.
• Power BI / Graph API – for custom compliance dashboards.

This turns static audit logs into active intelligence across your SOC and compliance teams.

Monitoring and Analysis Tools

Audit data is most valuable when combined with analytics , helping teams detect trends, not just incidents.

Real-World Tip

Turn audit into insight, not just evidence.
Don’t wait for a breach to check logs.
Use Audit and Activity Explorer regularly to identify patterns , repeated downloads, unusual access times, or policy bypass attempts.
Preventive review turns audit from reactive compliance into proactive security.

Exam Tip (SC-401)

Expect questions about:

• Differences between Audit Standard and Audit Premium
• Default vs extended retention periods
• Search-UnifiedAuditLog cmdlet usage
• Copilot and AI interaction logging
• Integration with DLP, Insider Risk, and eDiscovery

Example:

Which feature in Microsoft Purview Audit allows 10-year retention and high-value event logging?
Answer: Audit (Premium).

Best Practices

✅ Enable Audit Premium for regulated industries or long-term investigations.
✅ Assign the Audit Reader or Audit Manager roles appropriately.
✅ Regularly export key logs to secure storage or SIEM.
✅ Integrate with Insider Risk and Defender XDR for contextual investigations.
✅ Review audit retention quarterly to meet evolving compliance requirements.

Conclusion

Microsoft Purview Audit transforms every action in Microsoft 365 into an auditable, defensible event record.
It bridges operational transparency and legal assurance , ensuring you can reconstruct, verify, and prove any activity across your environment.

In a world where accountability defines compliance, Purview Audit isn’t optional , it’s essential.

In the next article, PUR512 – Smart Compliance: Using Activity Explorer, Content Explorer, and Compliance Manager Together, we’ll explore how to turn Purview’s audit data and reports into real-time insights for policy optimization and continuous compliance improvement.