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AWS EC2 Bulk User Data Enumeration

Identifies when the same AWS principal, from the same source IP, successfully calls EC2 "DescribeInstanceAttribute" for the "userData" attribute against more than 20 distinct instances within a 10-minute lookback.…

Description

Identifies when the same AWS principal, from the same source IP, successfully calls EC2 "DescribeInstanceAttribute" for the "userData" attribute against more than 20 distinct instances within a 10-minute lookback. Instance user data often contains bootstrap scripts and hardcoded credentials, so retrieving it across many instances in a short window can indicate reconnaissance or credential harvesting. Known CSPM roles, AWS service invocations, and Terraform calls from major cloud and carrier networks are excluded.

Detection logic

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Detection requirements

Platform
ContainersIaaSIdentity ProviderLinuxmacOSNetwork DevicesOffice SuiteSaaSWindows

The rule states no platform. This is derived from the 2 ATT&CK techniques it maps to.

Known benign triggers

  • Inventory jobs, configuration management, and security scanners that are not in the exclusion list may read `userData` across a large fleet. Confirm the principal ARN, source IP, ASN, and user agent against approved automation before treating the activity as malicious.
  • Terraform running from an ASN other than Amazon, Google, Microsoft, Verizon, or AT&T is still in scope. A large apply or refresh can exceed 20 instances.

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