Detection: Cloud API Calls From Previously Unseen User Roles

EXPERIMENTAL DETECTION

This detection status is set to experimental. The Splunk Threat Research team has not yet fully tested, simulated, or built comprehensive datasets for this detection. As such, this analytic is not officially supported. If you have any questions or concerns, please reach out to us at research@splunk.com.

Updated Date: 2025-05-02 ID: 2181ad1f-1e73-4d0c-9780-e8880482a08f Author: David Dorsey, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic detects cloud API calls executed by user roles that have not previously run these commands. It leverages the Change data model in Splunk to identify commands executed by users with the user_type of AssumedRole and a status of success. This activity is significant because new commands from different user roles can indicate potential malicious activity or unauthorized actions. If confirmed malicious, this behavior could lead to unauthorized access, data breaches, or other damaging outcomes by exploiting new or unmonitored commands within the cloud environment.

 1
 2| tstats earliest(_time) as firstTime, latest(_time) as lastTime from datamodel=Change where All_Changes.user_type=AssumedRole AND All_Changes.status=success by All_Changes.user, All_Changes.command All_Changes.object 
 3| `drop_dm_object_name("All_Changes")` 
 4| lookup previously_seen_cloud_api_calls_per_user_role user as user, command as command OUTPUT firstTimeSeen, enough_data 
 5| eventstats max(enough_data) as enough_data 
 6| where enough_data=1 
 7| eval firstTimeSeenUserApiCall=min(firstTimeSeen) 
 8| where isnull(firstTimeSeenUserApiCall) OR firstTimeSeenUserApiCall > relative_time(now(),"-24h@h") 
 9| table firstTime, user, object, command 
10|`security_content_ctime(firstTime)` 
11| `security_content_ctime(lastTime)`
12| `cloud_api_calls_from_previously_unseen_user_roles_filter`

Data Source

Name Platform Sourcetype Source
AWS CloudTrail AWS icon AWS 'aws:cloudtrail' 'aws_cloudtrail'

Macros Used

Name Value
security_content_ctime convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)
cloud_api_calls_from_previously_unseen_user_roles_filter search *
cloud_api_calls_from_previously_unseen_user_roles_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK
+ Kill Chain Phases
+ NIST
+ CIS
- Threat Actors
ID Technique Tactic
T1078 Valid Accounts Defense Evasion
Delivery
Exploitation
Installation
DE.AE
CIS 10

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting Value
Disabled true
Cron Schedule 0 * * * *
Earliest Time -70m@m
Latest Time -10m@m
Schedule Window auto
Creates Risk Event True
This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

Implementation

You must be ingesting your cloud infrastructure logs from your cloud provider. You should run the baseline search Previously Seen Cloud API Calls Per User Role - Initial to build the initial table of user roles, commands, and times. You must also enable the second baseline search Previously Seen Cloud API Calls Per User Role - Update to keep this table up to date and to age out old data. You can adjust the time window for this search by updating the cloud_api_calls_from_previously_unseen_user_roles_activity_window macro. You can also provide additional filtering for this search by customizing the cloud_api_calls_from_previously_unseen_user_roles_filter

Known False Positives

None.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

User $user$ of type AssumedRole attempting to execute new API calls $command$ that have not been seen before

Risk Object Risk Object Type Risk Score Threat Objects
user user 36 No Threat Objects

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation Not Applicable N/A N/A N/A
Unit ✅ Passing Dataset aws_cloudtrail aws:cloudtrail
Integration ✅ Passing Dataset aws_cloudtrail aws:cloudtrail

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: GitHub | Version: 5