What it does. Parse Office 365 Unified Audit Logs via Microsoft Graph API to detect Part of mukul975/Anthropic-Cybersecurity-Skills (817 security skills) (mukul975/Anthropic-Cybersecurity-Skills).

Install

• npx skills add mukul975/Anthropic-Cybersecurity-Skills --skill analyzing-office365-audit-logs-for-compromise, or copy the skill folder into ~/.claude/skills/analyzing-office365-audit-logs-for-compromise/.
• Raw file: curl -sL https://raw.githubusercontent.com/mukul975/Anthropic-Cybersecurity-Skills/HEAD/skills/analyzing-office365-audit-logs-for-compromise/SKILL.md

SKILL.md (verbatim)

name: analyzing-office365-audit-logs-for-compromise
description: Parse Office 365 Unified Audit Logs via Microsoft Graph API to detect
  email forwarding rule creation, inbox delegation, suspicious OAuth app grants, and
  other indicators of account compromise.
domain: cybersecurity
subdomain: cloud-security
tags:
- Office365
- Microsoft-Graph
- audit-logs
- email-compromise
- inbox-rules
- OAuth
- BEC
version: '1.0'
author: mahipal
license: Apache-2.0
nist_csf:
- PR.IR-01
- ID.AM-08
- GV.SC-06
- DE.CM-01
mitre_attack:
- T1114.002
- T1098.002
- T1556.006
- T1078.004

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.

When to Use

• When investigating security incidents that require analyzing office365 audit logs for compromise
• When building detection rules or threat hunting queries for this domain
• When SOC analysts need structured procedures for this analysis type
• When validating security monitoring coverage for related attack techniques

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

Other files in this skill

• LICENSE
• references/api-reference.md
• scripts/agent.py

references/api-reference.md (verbatim)

API Reference — Analyzing Office 365 Audit Logs for Compromise

Libraries Used

• msal: Microsoft Authentication Library — client credentials flow for Graph API
• requests: HTTP client for Graph API calls with pagination

CLI Interface

python agent.py --tenant-id T --client-id C --client-secret S audit-logs --days 7
python agent.py --tenant-id T --client-id C --client-secret S inbox-rules --user user@domain.com
python agent.py --tenant-id T --client-id C --client-secret S forwarding --user user@domain.com
python agent.py --tenant-id T --client-id C --client-secret S oauth
python agent.py --tenant-id T --client-id C --client-secret S full --users user1@d.com user2@d.com --days 7

Core Functions

get_access_token(tenant_id, client_id, client_secret) — MSAL auth

Uses ConfidentialClientApplication.acquire_token_for_client() with https://graph.microsoft.com/.default scope.

query_audit_logs(token, days) — Suspicious operation detection

Queries /auditLogs/directoryAudits for 11 suspicious operations: New-InboxRule, Set-InboxRule, Set-Mailbox, Add-MailboxPermission, UpdateInboxRules, New-TransportRule, etc.

check_inbox_rules(token, user_id) — Forwarding rule detection

GET /users/{id}/mailFolders/inbox/messageRules. Checks actions for forwardTo, forwardAsAttachmentTo, redirectTo. Flags external forwards and delete-after-forward patterns.

check_mailbox_forwarding(token, user_id) — SMTP forwarding check

GET /users/{id}/mailboxSettings. Checks auto-reply status and external audience.

check_oauth_grants(token) — OAuth consent audit

GET /oauth2PermissionGrants. Flags grants with Mail.Read, Mail.ReadWrite, Mail.Send, Files.ReadWrite.All, MailboxSettings.ReadWrite.

full_audit(token, users, days) — Comprehensive compromise analysis

Microsoft Graph Endpoints

Inbox Rule Risk Scoring

Suspicious Operations Monitored

New-InboxRule, Set-InboxRule, Set-Mailbox, Add-MailboxPermission, Set-MailboxJunkEmailConfiguration, Set-OwaMailboxPolicy, New-TransportRule, Add-RecipientPermission, Set-TransportRule, UpdateInboxRules, Set-MailboxAutoReplyConfiguration

Dependencies

• msal >= 1.24.0
• requests >= 2.28.0
• Azure AD app with AuditLog.Read.All, MailboxSettings.Read, Mail.Read

Back to mukul975/Anthropic-Cybersecurity-Skills (817 security skills) or Agent skills.