Detection: aws detect sts get session token abuse

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: 2024-05-14 ID: 85d7b35f-b8b5-4b01-916f-29b81e7a0551 Author: Rod Soto, Splunk Type: Hunting Product: Splunk Enterprise Security

Description

The following analytic identifies the suspicious use of the AWS STS GetSessionToken API call. It leverages CloudWatch logs to detect instances where this API is invoked, focusing on fields such as source IP address, event time, user identity, and status. This activity is significant because attackers can use these tokens to move laterally within the AWS environment and escalate privileges. If confirmed malicious, this could lead to unauthorized access and control over AWS resources, potentially compromising sensitive data and critical infrastructure.

Search

1`aws_cloudwatchlogs_eks` ASIA  userIdentity.type=IAMUser
2| spath eventName 
3| search eventName=GetSessionToken 
4| table sourceIPAddress eventTime userIdentity.arn userName userAgent user_type status region 
5| `aws_detect_sts_get_session_token_abuse_filter`

Data Source

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

Macros Used

Name	Value
aws_cloudwatchlogs_eks	`sourcetype="aws:cloudwatchlogs:eks"`
aws_detect_sts_get_session_token_abuse_filter	`search *`

aws_detect_sts_get_session_token_abuse_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
T1550	Use Alternate Authentication Material	Defense Evasion

KillChainPhase.EXPLOITAITON

NistCategory.DE_AE

Cis18Value.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	False

This configuration file applies to all detections of type hunting.

Implementation

You must install splunk AWS add-on and Splunk App for AWS. This search works with cloudwatch logs

Known False Positives

Sts:GetSessionToken can be very noisy as in certain environments numerous calls of this type can be executed. This search can be adjusted to provide specific values to identify cases of abuse. In specific environments the use of field requestParameters.serialNumber will need to be used.

Associated Analytic Story

AWS Cross Account Activity

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