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AWS EC2 Startup Script Modified on Stopped Instance

A successful EC2 StopInstances request was followed within one hour by a successful ModifyInstanceAttribute request targeting userData on the same instance, by the same IAM principal. This may indicate an attempt to…

Description

A successful EC2 StopInstances request was followed within one hour by a successful ModifyInstanceAttribute request targeting userData on the same instance, by the same IAM principal. This may indicate an attempt to change instance startup behavior or establish persistence. These CloudTrail events do not confirm that the modified user-data script executed.

Detection logic

Detection requirements

Platform
IaaS

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

Log source category
aws_cloudtrail

Known benign triggers

  • Authorized administrators and infrastructure automation may stop instances and update their user data. Review the IAM principal, instance, change window, and approved automation before escalating.

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