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Description

This search looks for AssumeRole events where an IAM role in a different account is requested for the first time.

  • Type: Anomaly
  • Product: Splunk Security Analytics for AWS, Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Authentication
  • Last Updated: 2020-05-28
  • Author: Rico Valdez, Splunk
  • ID: 21193641-cb96-4a2c-a707-d9b9a7f7792b

| tstats min(_time) as firstTime max(_time) as lastTime from datamodel=Authentication where Authentication.signature=AssumeRole by Authentication.vendor_account Authentication.user Authentication.src Authentication.user_role 
| `drop_dm_object_name(Authentication)` 
| rex field=user_role "arn:aws:sts:*:(?<dest_account>.*):" 
| where vendor_account != dest_account 
| rename vendor_account as requestingAccountId dest_account as requestedAccountId 
| lookup previously_seen_aws_cross_account_activity requestingAccountId, requestedAccountId, OUTPUTNEW firstTime 
| eval status = if(firstTime > relative_time(now(), "-24h@h"),"New Cross Account Activity","Previously Seen") 
|  where status = "New Cross Account Activity" 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)`
| `aws_cross_account_activity_from_previously_unseen_account_filter`

Associated Analytic Story

How To Implement

You must be ingesting your cloud infrastructure logs from your cloud provider. You should run the baseline search Previously Seen AWS Cross Account Activity - Initial to build the initial table of source IP address, geographic locations, and times. You must also enable the second baseline search Previously Seen AWS Cross Account Activity - Update to keep this table up to date and to age out old data. You can also provide additional filtering for this search by customizing the aws_cross_account_activity_from_previously_unseen_account_filter macro.

Required field

  • _time
  • Authentication.signature
  • Authentication.vendor_account
  • Authentication.user
  • Authentication.user_role
  • Authentication.src

Kill Chain Phase

  • Actions on Objectives

Known False Positives

Using multiple AWS accounts and roles is perfectly valid behavior. It's suspicious when an account requests privileges of an account it hasn't before. You should validate with the account owner that this is a legitimate request.

RBA

Risk Score Impact Confidence Message
15.0 30 50 AWS account $requestingAccountId$ is trying to access resource from some other account $requestedAccountId$, for the first time.

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

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