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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.

  • Type: Anomaly

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2020-07-21
  • Author: Bhavin Patel, Splunk
  • ID: 8d301246-fccf-45e2-a8e7-3655fd14379c

Annotations

ATT&CK
ID Technique Tactic
T1078.004 Cloud Accounts Defense Evasion, Initial Access, Persistence, Privilege Escalation
Kill Chain Phase
  • Actions on Objectives
NIST
  • DE.DP
  • DE.AE
CIS20
  • CIS 13
CVE 
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`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`

Macros

The SPL above uses the following Macros:

Note that abnormally_high_aws_instances_terminated_by_user_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required field

  • _time
  • eventName
  • errorCode
  • userName

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.

Associated Analytic story

RBA

Risk Score Impact Confidence Message
25.0 50 50 tbd

Reference

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

source | version: 2