Detection: AWS ECR Container Upload Unknown User

Updated Date: 2024-09-30 ID: 300688e4-365c-4486-a065-7c884462b31d Author: Patrick Bareiss, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic detects the upload of a new container image to AWS Elastic Container Registry (ECR) by an unknown user. It leverages AWS CloudTrail logs to identify PutImage events from the ECR service, filtering out known users. This activity is significant because container uploads should typically be performed by a limited set of authorized users. If confirmed malicious, this could indicate unauthorized access, potentially leading to the deployment of malicious containers, data exfiltration, or further compromise of the AWS environment.

Search

1`cloudtrail` eventSource=ecr.amazonaws.com eventName=PutImage NOT `aws_ecr_users` 
2| rename requestParameters.* as * 
3| rename repositoryName AS image 
4| eval phase="release" 
5| eval severity="high" 
6| stats min(_time) as firstTime max(_time) as lastTime by awsRegion, eventName, eventSource, user, userName, src_ip, imageTag, registryId, image, phase, severity 
7| `security_content_ctime(firstTime)` 
8| `security_content_ctime(lastTime)` 
9| `aws_ecr_container_upload_unknown_user_filter`

Data Source

Name	Platform	Sourcetype	Source
AWS CloudTrail PutImage	AWS	`'aws:cloudtrail'`	`'aws_cloudtrail'`

Macros Used

Name	Value
aws_ecr_users	`userName IN (user)`
aws_ecr_container_upload_unknown_user_filter	`search *`

aws_ecr_container_upload_unknown_user_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
T1204.003	Malicious Image	Execution
T1204	User Execution	Execution

KillChainPhase.INSTALLATION

NistCategory.DE_AE

Cis18Value.CIS_13

TeamTNT

LAPSUS$

Scattered Spider

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 splunk AWS add on and Splunk App for AWS. This search works with AWS CloudTrail logs.

Known False Positives

unknown

Associated Analytic Story

Dev Sec Ops

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
Container uploaded from unknown user $user$	49	70	70

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

References

https://attack.mitre.org/techniques/T1204/003/

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	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: 3