Microsoft Sentinel Integration with M365

Microsoft Sentinel is a cloud-native Security Information and Event Management (SIEM) and Security Orchestration Automation and Response (SOAR) solution. It provides intelligent security analytics and threat intelligence across an enterprise, enabling proactive threat detection, investigation, and automated response. Sentinel exists to address the limitations of traditional on-premises SIEMs: high infrastructure costs, complex scaling, and siloed data. By being cloud-native, Sentinel offers elastic scalability, built-in AI, and deep integration with Microsoft 365 and Azure services.

Sentinel ingests data from Microsoft 365 sources using built-in data connectors. These connectors pull logs from: - Azure Active Directory (Azure AD): Sign-in logs, audit logs, and provisioning logs. - Microsoft 365 Defender: Alerts from Defender for Endpoint, Defender for Office 365, Defender for Identity, and Defender for Cloud Apps. - Office 365: Exchange Online, SharePoint Online, Teams, and OneDrive audit logs. - Microsoft Cloud App Security (MCAS): Alerts and activity logs. - Azure Information Protection: Data classification and labeling logs.

The connectors work by subscribing to Microsoft 365’s unified audit logging and streaming data via the Office 365 Management Activity API. Data is stored in the Log Analytics workspace associated with Sentinel.

Step 1: Data Ingestion - Connectors pull logs from Microsoft 365 APIs every few minutes (typically 5-15 minutes depending on the service). - Logs are normalized to the Common Event Format (CEF) or Sentinel’s schema.

Step 2: Data Retention - By default, logs are retained for 90 days in the Log Analytics workspace. You can adjust retention up to 2 years or export to Azure Storage for longer retention. - Sentinel itself does not charge for storage; you pay for Log Analytics data ingestion and retention.

Step 3: Detection - Analytics rules run on a schedule (e.g., every 5 minutes) or in near real-time using alert triggers. - Rules can use Kusto Query Language (KQL) to query logs. Example: A rule to detect multiple failed sign-ins followed by a successful sign-in from a different country.

Step 4: Incident Creation - When a rule matches, Sentinel creates an incident with severity, status, and entities (users, IPs, devices). - Incidents can be automatically assigned to analysts based on severity.

Step 5: Investigation and Response - Analysts use the investigation graph to visualize relationships between entities. - Playbooks can be triggered manually or automatically. For example, a playbook could send an email to the user’s manager and block the user’s account via Microsoft Graph API.

To configure an Azure AD connector: 1. In Sentinel, navigate to Data connectors > Azure Active Directory. 2. Click "Open connector page". 3. Select the log types: Sign-in logs and Audit logs. 4. Click "Connect". 5. Verify by checking the "Data received" graph; it may take up to 15 minutes for data to appear.

To verify logs are flowing:

SigninLogs
| where TimeGenerated > ago(1h)
| count

Contoso Corp, a multinational with 50,000 employees, uses Microsoft 365 E5 and needs to detect insider threats where employees exfiltrate data via email or SharePoint. They deploy Sentinel with Office 365 and Azure AD connectors. They create an analytics rule that triggers when a user downloads more than 100 files from SharePoint within an hour and then sends an email with attachments to an external domain. Sentinel creates an incident, and a playbook automatically blocks the user's account and sends a notification to the manager. This scenario requires careful tuning of thresholds to avoid false positives from legitimate bulk downloads. Performance-wise, Sentinel handles millions of logs daily; the key is to optimize KQL queries to run within 5 minutes. Misconfiguration example: If the Office 365 connector is not granted sufficient permissions, logs will not stream, causing missed detections.

Fabrikam Inc, a mid-sized company with 2,000 users, experiences frequent phishing attacks. They use Microsoft 365 Defender for email protection and Sentinel for correlation. When Defender detects a phishing email, it sends an alert to Sentinel. Sentinel's analytics rule correlates that alert with sign-in logs: if a user who received the phishing email later signs in from an unusual location, Sentinel creates a high-severity incident. A playbook then disables the user's account and deletes the phishing email from all mailboxes via Microsoft Graph. This integration reduces response time from hours to minutes. A common mistake is not enabling the Microsoft 365 Defender connector in Sentinel, causing alerts to be missed. Also, if the playbook fails due to Graph API throttling, the account may not be disabled promptly. Fabrikam mitigates this by setting up retry logic in the Logic App.

Northwind Traders, a financial services firm, must retain audit logs for two years for regulatory compliance. They use Sentinel with Office 365 audit logs and set Log Analytics retention to 730 days. They create a workbook that shows all administrative actions in Exchange Online and SharePoint. Sentinel’s built-in ‘Sensitive Data Discovery’ workbook helps identify potential compliance violations. They also use Sentinel’s Fusion analytics to detect advanced attacks. Scaling consideration: At 10 TB of logs per month, they use Azure Storage archives for logs older than 90 days to reduce costs. A frequent issue is that some audit logs (e.g., Teams) are not enabled by default; they must be enabled in the Microsoft 365 Compliance Center. Without that, Sentinel receives incomplete data, leading to compliance gaps.