Analyzing Office 365 Audit Logs for Compromise

Overview

Business Email Compromise (BEC) attacks often leave traces in Office 365 audit logs: suspicious inbox rule creation, email forwarding to external addresses, mailbox delegation changes, and unauthorized OAuth application consent grants. This skill uses the Microsoft Graph API to query the Unified Audit Log, enumerate inbox rules across mailboxes, detect forwarding configurations, and identify compromised account indicators.

Prerequisites

• Azure AD app registration with AuditLog.Read.All, MailboxSettings.Read, Mail.Read (application permissions)
• Python 3.9+ with msal, requests
• Client secret or certificate for authentication
• Global Reader or Security Reader role

Steps

1. Authenticate to Microsoft Graph using MSAL client credentials flow
2. Query Unified Audit Log for suspicious operations (Set-Mailbox, New-InboxRule)
3. Enumerate inbox rules across mailboxes and flag forwarding rules
4. Detect mailbox delegation changes (Add-MailboxPermission)
5. Identify OAuth consent grants to suspicious applications
6. Check for suspicious sign-in patterns from audit logs
7. Generate compromise indicator report with timeline

Expected Output

• JSON report listing forwarding rules, delegation changes, OAuth grants, and suspicious audit events with risk scores
• Timeline of compromise indicators with affected mailboxes

Verification Criteria

Confirm successful execution by validating:

• [ ] All prerequisite tools and access requirements are satisfied
• [ ] Each workflow step completed without errors
• [ ] Output matches expected format and contains expected data
• [ ] No security warnings or misconfigurations detected
• [ ] Results are documented and evidence is preserved for audit

Compliance Framework Mapping

This skill supports compliance evidence collection across multiple frameworks:

• SOC 2: CC6.1 (Logical Access), CC6.6 (System Boundaries), CC7.1 (Monitoring)
• ISO 27001: A.8.1 (Asset Management), A.13.1 (Network Security), A.14.1 (System Acquisition)
• NIST 800-53: AC-3 (Access Enforcement), SC-7 (Boundary Protection), CM-7 (Least Functionality)
• NIST CSF: PR.AC (Access Control), PR.DS (Data Security), DE.CM (Continuous Monitoring)

Claw GRC Tip: When this skill is executed by a registered agent, compliance evidence is automatically captured and mapped to the relevant controls in your active frameworks.

Deploying This Skill with Claw GRC

Agent Execution

Register this skill with your Claw GRC agent for automated execution:

# Install via CLI
npx claw-grc skills add analyzing-office365-audit-logs-for-compromise

# Or load dynamically via MCP
grc.load_skill("analyzing-office365-audit-logs-for-compromise")

Audit Trail Integration

When executed through Claw GRC, every step of this skill generates tamper-evident audit records:

• SHA-256 chain hashing ensures no step can be modified after execution
• Evidence artifacts (configs, scan results, logs) are automatically attached to relevant controls
• Trust score impact — successful execution increases your agent's trust score

Continuous Compliance

Schedule this skill for recurring execution to maintain continuous compliance posture. Claw GRC monitors for drift and alerts when re-execution is needed.