Abnormally High AWS Instances Terminated by User

Name:Abnormally High AWS Instances Terminated by User
id:8d301246-fccf-45e2-a8e7-3655fd14379c
version:4
date:2024-10-17
author:Bhavin Patel, Splunk
status:deprecated
type:Anomaly
Description:This search looks for AWS CloudTrail events where an abnormally high number of instances were successfully terminated by a user in a 10-minute window. This search is deprecated and have been translated to use the latest Change Datamodel.
Data_source:

search:`cloudtrail` eventName=TerminateInstances errorCode=success
| bucket span=10m _time
| stats count AS instances_terminated by _time userName
| eventstats avg(instances_terminated) as total_terminations_avg, stdev(instances_terminated) as total_terminations_stdev
| eval threshold_value = 4
| eval isOutlier=if(instances_terminated > total_terminations_avg+(total_terminations_stdev * threshold_value), 1, 0)
| search isOutlier=1 AND _time >= relative_time(now(), "-10m@m")| eval num_standard_deviations_away = round(abs(instances_terminated - total_terminations_avg) / total_terminations_stdev, 2) |table _time, userName, instances_terminated, num_standard_deviations_away, total_terminations_avg, total_terminations_stdev
| `abnormally_high_aws_instances_terminated_by_user_filter`

how_to_implement:You must install the AWS App for Splunk (version 5.1.0 or later) and Splunk Add-on for AWS (version 4.4.0 or later), then configure your AWS CloudTrail inputs.
known_false_positives:Many service accounts configured with your AWS infrastructure are known to exhibit this behavior. Please adjust the threshold values and filter out service accounts from the output. Always verify whether this search alerted on a human user.
References:
drilldown_searches:
  :
tags:
  analytic_story:
    - 'Suspicious AWS EC2 Activities'
  asset_type:AWS Instance
  confidence:50
  impact:50
  message:tbd
  mitre_attack_id:
    - 'T1078.004'
  observable:
    name:'userName'
    type:'User'
    - role:
      - 'Victim'
  product:
    - 'Splunk Enterprise'
    - 'Splunk Enterprise Security'
    - 'Splunk Cloud'
  required_fields:
    - '_time'
    - 'eventName'
    - 'errorCode'
    - 'userName'
  risk_score:25
  security_domain:network

tests:
  :
manual_test:None