Anomalous S3 bucket activity from user ARN

Goal

Detect when an AWS user performs S3 bucket write activities they do not usually perform.

Strategy

Monitor cloudtrail logs for S3 Data Plane events (@eventCategory:Data) to detect when an AWS User (@userIdentity.arn) is detected performing anomalous S3 Write (@evt.name:(Abort* OR Create* OR Delete* OR Initiate* OR Put* OR Replicate* OR Update*)) API calls.

Triage and response

  1. Determine if user: {{@userIdentity.arn}} should be performing the: {{@evt.name}} API calls.
    • Use the Cloud SIEM - User Investigation dashboard to assess user activity.
  2. If not, investigate the user: {{@userIdentity.arn}} for indicators of account compromise and rotate credentials as necessary.

Changelog

27 October 2022 - Updated tags.