Detection: AWS ECR Container Upload Unknown User

Updated Date: 2025-02-10 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.

1`cloudtrail` eventSource=ecr.amazonaws.com eventName=PutImage NOT `aws_ecr_users` 
2| rename requestParameters.* as * 
3| rename repositoryName AS image 
4| rename user_name as user 
5| stats count min(_time) as firstTime max(_time) as lastTime by signature user user_agent src vendor_account vendor_region vendor_product image 
6| `security_content_ctime(firstTime)` 
7| `security_content_ctime(lastTime)` 
8| `aws_ecr_container_upload_unknown_user_filter`

Data Source

Name Platform Sourcetype Source
AWS CloudTrail PutImage AWS icon 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
Installation
DE.AE
CIS 13

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

Risk Based Analytics (RBA)

Risk Message:

Container uploaded from unknown user $user$

Risk Object Risk Object Type Risk Score Threat Objects
user user 49 src

References

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: 6