Detection: Detect new API calls from user roles

DEPRECATED DETECTION

This detection has been marked as deprecated by the Splunk Threat Research team. This means that it will no longer be maintained or supported. If you have any questions or concerns, please reach out to us at research@splunk.com.

Updated Date: 2024-08-19 ID: 22773e84-bac0-4595-b086-20d3f335b4f1 Author: Bhavin Patel, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

This search detects new API calls that have either never been seen before or that have not been seen in the previous hour, where the identity type is AssumedRole.

Search

 1`cloudtrail` eventType=AwsApiCall errorCode=success userIdentity.type=AssumedRole [search `cloudtrail` eventType=AwsApiCall errorCode=success  userIdentity.type=AssumedRole 
 2| stats earliest(_time) as earliest latest(_time) as latest by userName eventName 
 3|  inputlookup append=t previously_seen_api_calls_from_user_roles 
 4| stats min(earliest) as earliest, max(latest) as latest by userName eventName 
 5| outputlookup previously_seen_api_calls_from_user_roles
 6| eval newApiCallfromUserRole=if(earliest>=relative_time(now(), "-70m@m"), 1, 0) 
 7| where newApiCallfromUserRole=1 
 8| `security_content_ctime(earliest)` 
 9| `security_content_ctime(latest)` 
10| table eventName userName]  
11|rename userName as user
12| stats values(eventName) earliest(_time) as earliest latest(_time) as latest by user 
13| `security_content_ctime(earliest)` 
14| `security_content_ctime(latest)` 
15| `detect_new_api_calls_from_user_roles_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
N/A	N/A	N/A	N/A	N/A

Macros Used

Name	Value
cloudtrail	`sourcetype=aws:cloudtrail`
detect_new_api_calls_from_user_roles_filter	`search *`

detect_new_api_calls_from_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
T1078.004	Cloud Accounts	Defense Evasion

KillChainPhase.DELIVERY

KillChainPhase.EXPLOITAITON

KillChainPhase.INSTALLATION

NistCategory.DE_AE

Cis18Value.CIS_10

APT28

APT29

APT33

APT5

Ke3chang

LAPSUS$

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 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. This search works best when you run the "Previously seen API call per user roles in AWS CloudTrail" support search once to create a history of previously seen user roles.

Known False Positives

It is possible that there are legitimate user roles making new or infrequently used API calls in your infrastructure, causing the search to trigger.

Associated Analytic Story

AWS User Monitoring

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
tbd	25	50	50

The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	Not Applicable	N/A	N/A	N/A
Unit	❌ Failing	N/A	`N/A`	`N/A`
Integration	❌ Failing	N/A	`N/A`	`N/A`

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: 2