Elastic high stable kql

AWS EC2 Stop, Start, and User Data Modification Correlation

Identifies a short sequence of EC2 management APIs against the same instance that is consistent with modifying instance user data and forcing it to run on the next boot: `ModifyInstanceAttribute` with user data, followed by stop and start. Adversaries may update `userData` and cycle instance state so malicious scripts execute as root on Linux or as the system context on Windows. This rule correlates successful `StopInstances`, `StartInstances`, and `ModifyInstanceAttribute` events that reference `userData` within a five-minute window, grouped by instance, `user.name`, account, source IP, and user agent. A hit requires exactly three distinct API names in that bucket.

View Source

Detection Logic

FROM logs-aws.cloudtrail-*
| WHERE event.provider == "ec2.amazonaws.com" 
    and event.outcome == "success"
    and aws.cloudtrail.user_identity.type != "AWSService"
    and not (
      user_agent.original like "*Terraform*"
      or user_agent.original like "*Ansible*"
      or user_agent.original like "*Pulumi*"
    ) and not source.address in ("cloudformation.amazonaws.com", "servicecatalog.amazonaws.com")
    and
  (
   event.action in ("StopInstances", "StartInstances") or 
   (event.action == "ModifyInstanceAttribute" and aws.cloudtrail.request_parameters like "*userData=*")
   )
| grok aws.cloudtrail.request_parameters """instanceId=(?<Esql.instance_id>[^,}\]]+)"""
| STATS Esql.event_action_unique_count = COUNT_DISTINCT(event.action), 
        Esql.event_action_values = VALUES(event.action) by Esql.instance_id, user.name, cloud.account.id, Esql.time_bucket = DATE_TRUNC(5 minute, @timestamp) , user_agent.original, source.ip, source.as.organization.name, source.geo.country_name
| where Esql.event_action_unique_count == 3
| Keep Esql.*, user.name, cloud.account.id, user_agent.original, source.ip, source.as.organization.name, source.geo.country_name

False Positives

  • ⚠ Legitimate automation or administrators may change user data and restart instances during maintenance, image baking, or configuration fixes. Review the caller identity, change tickets, and whether `user_agent.original` and `source.ip` match known tooling and networks (the rule groups on both together with `user.name`).

Field Validations

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