Monitoring Azure AD Sign-in Logs: A Comprehensive Guide

In today's cloud-centric world, understanding who is accessing your resources and when is paramount. Azure Active Directory (Azure AD) provides robust sign-in logging capabilities that are indispensable for security monitoring, troubleshooting, and auditing. This guide will walk you through the essentials of monitoring these logs to maintain a secure and compliant environment.

Why Monitor Azure AD Sign-in Logs?

• Security Threat Detection: Identify suspicious login activities such as impossible travel, brute-force attacks, and logins from unfamiliar locations.
• User Behavior Analysis: Gain insights into how users interact with your applications and services.
• Troubleshooting Login Issues: Quickly diagnose and resolve problems users might encounter during sign-in.
• Compliance and Auditing: Meet regulatory requirements by maintaining a detailed log of access events.
• Performance Monitoring: Track sign-in success and failure rates to ensure optimal user experience.

Accessing Sign-in Logs

You can access Azure AD sign-in logs directly from the Azure portal:

1. Navigate to the Azure portal.
2. Search for and select "Azure Active Directory".
3. Under the "Monitoring & health" section, choose "Sign-in logs".

The sign-in logs provide a wealth of information, including:

• User: The user who signed in.
• Application: The application accessed.
• IP Address: The source IP address of the sign-in attempt.
• Location: The geographical location derived from the IP address.
• Status: Success or Failure.
• Authentication Details: The type of authentication used.
• Device Information: Details about the device used.

Key Fields to Watch For:

When reviewing sign-in logs, pay close attention to the following fields:

• IP Address: Look for IPs from unexpected or known malicious sources.
• Location: Identify sign-ins from unusual geographical locations, especially if the user is not known to travel there.
• Status: Analyze failure reasons to troubleshoot access problems or detect brute-force attempts.
• User Agent: Can indicate the browser or client application used.

Leveraging Azure AD Sign-in Log Data

1. Filtering and Searching

The Azure portal offers powerful filtering capabilities. You can filter by:

• Date and Time
• User Name
• Application
• Status (Success, Failure)
• IP Address
• Location

This allows you to narrow down the logs to investigate specific events or patterns.

2. Correlating with Other Logs

For a complete security picture, correlate Azure AD sign-in logs with other Azure AD logs, such as:

• Audit Logs: Track changes to Azure AD resources.
• Provisioning Logs: Monitor user and group provisioning.

3. Exporting Logs

You can export sign-in logs for long-term storage, analysis in external tools, or integration with SIEM (Security Information and Event Management) solutions. Common export options include:

• Azure Monitor Logs (Log Analytics): This is the recommended approach for continuous monitoring and advanced analytics.
• CSV: For quick analysis or manual review.

Setting up Azure Monitor Logs (Log Analytics)

To send sign-in logs to Azure Monitor Logs, follow these steps:

1. In Azure AD, go to "Diagnostic settings".
2. Click "Add diagnostic setting".
3. Select "Sign-in logs" and "Audit logs" (recommended).
4. Choose "Send to Log Analytics workspace" and select your workspace.
5. Save the setting.

Once data is in Log Analytics, you can write Kusto Query Language (KQL) queries to perform sophisticated analysis. For example:

            SigninLogs
            | where TimeGenerated > ago(1d)
            | where ResultType != 0 // Filter for failures
            | project TimeGenerated, UserPrincipalName, AppDisplayName, Location, FailureReason
            | summarize count() by UserPrincipalName, Location, FailureReason
            | order by count_ desc
            

Common Scenarios and What to Look For

1. Suspicious Sign-ins

• Multiple Failed Sign-ins: Could indicate a brute-force attack. Look for the same user and IP address attempting to log in repeatedly.
• Impossible Travel: A user logging in from two distant locations within an unreasonably short timeframe.
• Sign-ins from Unknown Locations: Users logging in from countries or regions they don't typically operate from.

2. Troubleshooting User Access

If a user reports they cannot access an application:

• Filter the sign-in logs for that specific user and the relevant application.
• Check the "Status" column for "Failure". The "Failure Reason" field will provide crucial details (e.g., incorrect password, multi-factor authentication requirement not met).

Conclusion

Monitoring Azure AD sign-in logs is a critical component of a robust cloud security strategy. By understanding how to access, interpret, and leverage this data, you can proactively identify threats, troubleshoot issues, and ensure the security and compliance of your Azure environment. Make it a regular practice to review your sign-in logs, and consider automating alerts for suspicious activities to stay ahead of potential security breaches.