Investigation Copilot: Microsoft Purview for AI Audit and Evidence

Introduction

Enabling Copilot without audit is deploying without a safety net. While most organizations focus on prevention via DLP, true maturity lies in the ability to investigate post-incident. Microsoft Purview offers a complete arsenal to audit, investigate and gather evidence around Copilot activity and AI agents.

The issue is no longer whether your users will interact with AI, but how you will document and investigate those interactions when compliance requires it.

Auditable Copilot Events in Microsoft Purview

Copilot Audit Architecture

Microsoft Purview Audit now captures Copilot interactions with forensic-level detail. Events are stored in unified audit logs with a default retention of 90 days (extensible to 10 years with appropriate licenses).

Critical Audit Fields

Copilot events in Purview contain investigation-specific fields:

• PromptText: Exact content of user prompt
• ResponseSummary: Summary of generated response
• SourceDocuments: M365 documents referenced
• SensitivityScore: Calculated sensitivity score
• UserContext: Application and usage context
• ProcessingTime: Processing duration (anomaly indicator)

KQL Investigation Query

1OfficeActivity
2| where Operation == "CopilotInteraction"
3| where TimeGenerated > ago(30d)
4| extend PromptLength = strlen(PromptText)
5| where PromptLength > 500 or SensitivityScore > 0.7
6| project TimeGenerated, UserId, PromptText, SensitivityScore, SourceDocuments
7| order by SensitivityScore desc

Five Copilot Investigation Scenarios

1. Sensitive Data in Prompts

When a user includes confidential information directly in their Copilot prompts, Communication Compliance can trigger alerts based on sensitive content rules.

2. Abnormal Volume of Copilot Requests

Volume anomalies may indicate data exfiltration or unauthorized use. Behavioral analysis becomes critical.

1OfficeActivity
2| where Operation == "CopilotInteraction"
3| summarize RequestCount = count() by UserId, bin(TimeGenerated, 1h)
4| where RequestCount > 100
5| join (OfficeActivity | where Operation == "FileDownloaded") on UserId
6| project UserId, RequestCount, FileDownloads = count_

3. Exfiltration via Copilot

Copilot can potentially be used to reformat or summarize sensitive documents before exfiltration. Insider Risk Management correlates these weak signals.

4. eDiscovery of Copilot Conversations

Copilot interactions are now included in the eDiscovery scope. Conversations can be placed under legal hold and subject to advanced searches.

5. AI-Related Insider Risk Indicators

Insider Risk Management integrates Copilot metrics into its anomaly detection models, correlating AI usage with other behavioral indicators.

Communication Compliance for Artificial Intelligence

Coverage Scope

Communication Compliance monitors Copilot interactions in:

• Microsoft Teams (integrated Copilot)
• Outlook (writing assistance)
• Word, PowerPoint, Excel (content suggestions)
• Copilot Studio (custom agents)

RBAC Architecture and Privacy

Monitoring AI interactions raises specific privacy questions. Implementation must respect:

• Role Separation: Compliance analysts cannot access prompts without justification
• Auditor Audit: Any consultation of Copilot interaction is itself audited
• Anonymization: Ability to mask user identity for trend analysis

Building a Minimum Evidence Package

Retention Strategy

Building digital evidence around Copilot requires a consistent retention strategy:

• Audit logs: 12 months minimum (24 months recommended)
• Complete interactions: 6 months for at-risk users
• Anonymized metadata: 36 months for trend analysis
• Evidence under legal hold: Full procedural duration

SOC/Incident Response Runbook

The Copilot investigation process must integrate into existing runbooks:

Copilot Investigation Operational Checklist

• ☐ Enable Copilot audit in Microsoft Purview Audit
• ☐ Configure Communication Compliance policies for AI interactions
• ☐ Integrate Copilot into Insider Risk Management scenarios
• ☐ Extend audit retention to 12+ months
• ☐ Train SOC teams on AI investigation specifics
• ☐ Define RBAC access levels for Copilot data
• ☐ Test eDiscovery capabilities on Copilot conversations
• ☐ Document AI-specific legal hold procedures
• ☐ Implement Copilot × other data source correlations
• ☐ Validate cryptographic integrity of exported evidence

Common Errors in Copilot Investigation

1. Confusion Between DLP and Audit

2. Insufficient Retention

Complex investigations may require data spanning 12-18 months. The default 90-day retention is insufficient for most forensic scenarios.

3. Neglect of Application Context

An isolated Copilot interaction may appear harmless. It is the complete sequence that reveals malicious intent.

4. Absence of Multi-Source Correlation

Copilot must be investigated in correlation with Cloud App Security, Azure AD logs, and file sharing events.

5. Underestimation of Privacy Issues

User prompts may contain sensitive personal information requiring specific protections.

30/60/90 Day Deployment Plan

First 30 Days: Foundations

• Enable Copilot audit across all M365 workloads
• Initial Communication Compliance configuration
• Train compliance teams on new capabilities
• Test basic KQL queries

60 Days: Operationalization

• Deploy Insider Risk policies integrating Copilot
• Implement correlations with other data sources
• Conduct first investigations on simulated cases
• Adjust alert thresholds based on observed patterns

90 Days: Maturity

• Complete integration into incident response runbooks
• Deploy eDiscovery capabilities for Copilot
• Third-party audit of investigation processes
• Complete documentation of legal procedures

Conclusion: Investigation as Competitive Advantage

Copilot investigation capability becomes a competitive differentiator for mature organizations. Beyond simple compliance, it is the building of cyber resilience that integrates AI into its protection perimeter.

Implementing Microsoft Purview for Copilot audit is not limited to checking a compliance box: it is building the trust necessary for massive AI adoption in the enterprise.

Your next step? Assess your current maturity and implement the 30/60/90 day plan. Copilot investigation is no longer optional, it is mandatory.

Glossary of Technical Terms

Communication Compliance: Microsoft Purview service for monitoring internal communications to detect policy violations.

eDiscovery: Process of identifying, collecting and producing electronic data in legal proceedings.

Insider Risk Management: Solution for detecting risky behavior by internal users based on behavioral analysis.

KQL (Kusto Query Language): Query language used for data analysis in the Microsoft ecosystem.

Legal Hold: Process of preserving electronic data to meet legal obligations.

RBAC (Role-Based Access Control): Access control model based on organizational roles.

Practical PowerShell Scripts

Copilot Audit Activation Script

1# Connect to Security and Compliance Center
2Connect-IPPSSession
3 
4# Enable audit for Copilot events
5Set-AdminAuditLogConfig -UnifiedAuditLogIngestionEnabled $true
6Set-OrganizationConfig -AuditDisabled $false
7 
8# Configure extended retention
9New-UnifiedAuditLogRetentionPolicy -Name "CopilotAudit-12Months" -Priority 1 -RecordTypes CopilotInteraction -RetentionDuration TenYears

Automated Audit Search

1# Search for suspicious Copilot interactions
2$startDate = (Get-Date).AddDays(-30)
3$endDate = Get-Date
4 
5Search-UnifiedAuditLog -StartDate $startDate -EndDate $endDate -RecordType CopilotInteraction -Operations "CopilotPrompt","CopilotResponse" -ResultSize 5000 | Where-Object {
6    $_.AuditData -match '"SensitivityScore":[0-9]\.[7-9]|[1-9]\.[0-9]'
7} | Export-Csv -Path "C:\Audit\CopilotHighRisk.csv" -NoTypeInformation

Useful Links and Official References

Official Microsoft Documentation:

1. Microsoft Purview Audit (Premium) - Complete documentation on advanced audit capabilities
2. Communication Compliance in Microsoft Purview - Configuration and usage guide
3. Microsoft Purview eDiscovery (Premium) - Investigation and evidence collection process
4. Insider Risk Management - Detection and investigation of internal risks

Complementary Technical Resources:

• KQL Reference for Microsoft Sentinel
• PowerShell for Microsoft Purview
• Microsoft 365 Audit Log Schema