Azure Suspicious VM Scale Set Extension Installation

Triggers

• A Microsoft Entra Identity is using a highly permissive role within a Resource Group or Subscription scope to install and execute an extension within a VM Scale Set (VMSS) without explicit consent or an audit trail. This is unusual for the identity.

Possible Root Causes

• Unauthorized Access: An attacker has gained access to a Microsoft Entra Identity and is using it to install extensions on VM Scale Sets without permission.
• Misconfigured Security Settings: A Microsoft Entra Identity has been granted excessive permissions, allowing them to install extensions on VM Scale Sets.
• Malware or Vulnerability Exploitation: An attacker is using malware or exploiting a vulnerability in the VM�s operating system to escalate privileges and install high-risk extensions.
• Human Error: Mistakes during VM Scale Set management or maintenance have led to unintended installations.
• Legitimate Administrative Action: A valid identity, which typically does not interact with VM Scale Set extensions, is installing an extension to fulfill a job function.

Business Impact

• Data loss or corruption due to unauthorized access.
• System compromise or ransomware attacks.
• Unplanned changes, service disruptions, or downtime for critical services.
• Compliance and regulatory issues due to inadequate security controls.

Steps to Verify

• Investigate the user or service principal responsible for the deployment. Review the identity for any signs of unauthorized access or excessive privileges.
• Analyze Extension Parameters: Examine the parameters used in the extension installation to identify potential security risks, such as the deletion of sensitive data.
• Check Execution Time and Frequency: Review the Azure Activity Logs to verify if the suspicious extension installations are occurring within regular business hours or if multiple instances are occurring within a short timeframe.
• Review VM Scale Set (VMSS) Configuration and Permissions: Ensure that the VMSS�s configuration and permissions align with organizational security policies.
• Conduct a thorough security audit and risk assessment to identify vulnerabilities and implement necessary remediation actions.