Introduction

Microsoft Defender for Identity (MDI), formerly known as Azure Advanced Threat Protection (ATP), is a critical component in the cybersecurity arsenal for detecting and investigating threats within an enterprise network. One of the common alerts generated by MDI is the Enumeration Alert, which signals potentially malicious scanning activities on your network. Investigating these alerts is crucial for maintaining network security and integrity. This article guides you through the process of investigating enumeration alerts in MDI.

Understanding Enumeration Alerts

Enumeration alerts in MDI are triggered when there are attempts to discover information about your network or domain, such as user accounts or domain controllers. This behavior is often a precursor to more serious attacks and may indicate a breach or a reconnaissance effort by attackers.

Step 1: Analyze the Alert Details

The first step in your investigation is to review the alert details. MDI provides comprehensive information about each alert, including the time of detection, the affected systems, and the nature of the suspicious activity. Pay attention to:

• Source IP address: Identifies where the enumeration is coming from.
• Targeted resources: Shows which parts of the network are being scanned.
• Enumeration technique: Indicates the method used for the scanning, such as LDAP queries or SMB shares.

Step 2: Contextualize the Alert

Context is key in determining the severity and intent of the enumeration. Consider the following:

• Is the source IP internal or external? Internal sources might indicate a compromised insider, while external sources could suggest an outside attack.
• Have there been similar incidents recently? Recurring alerts from the same source or targeting the same resources might indicate a targeted attack.
• Is the enumeration part of a legitimate process? Sometimes, enumeration activities are part of normal network operations or maintenance tasks.

Step 3: Correlate with Other Security Tools

Integrate MDI with other security tools such as firewalls, SIEM systems, or endpoint protection platforms. This integration allows you to correlate the enumeration alert with other security events and gain a more comprehensive view of the situation.

Step 4: Investigate the Source

Once you have a better understanding of the alert:

• Examine the source system: If the source is internal, check if the system has been compromised or if a legitimate user account has been misused.
• Analyze network traffic: Look for unusual patterns or communications with known malicious IP addresses or domains.

Step 5: Remediate and Respond

Based on your investigation, take appropriate actions:

• If the alert is a false positive, adjust MDI policies to reduce future false alarms.
• If the alert is malicious, initiate your incident response protocol. This might include isolating affected systems, changing compromised credentials, and further monitoring for suspicious activities.

Step 6: Learn and Adapt

Every investigation offers learning opportunities. Update your security policies and configurations to prevent similar incidents. Train your team based on the insights gained, and continuously adapt to the evolving threat landscape.

Conclusion

Investigating enumeration alerts in MDI is a vital part of maintaining network security. By following a structured approach, organizations can effectively respond to these alerts, mitigate threats, and enhance their overall security posture. Remember, proactive measures, continuous monitoring, and a well-prepared response plan are key to staying ahead of cyber threats.