AWS ECR Container Upload Unknown User

SPLUNK detection rule by Patrick Bareiss, Splunk · Apache-2.0

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.

name: AWS ECR Container Upload Unknown User
id: 300688e4-365c-4486-a065-7c884462b31d
version: 12
creation_date: '2021-08-19'
modification_date: '2026-05-13'
author: Patrick Bareiss, Splunk
status: production
type: Anomaly
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.
data_source:
    - AWS CloudTrail PutImage
search: |-
    `cloudtrail` eventSource=ecr.amazonaws.com eventName=PutImage NOT `aws_ecr_users`
      | rename requestParameters.* as *
      | rename repositoryName AS image
      | rename user_name as user
      | stats count min(_time) as firstTime max(_time) as lastTime
        BY signature user user_agent
           src vendor_account vendor_region
           vendor_product image
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `aws_ecr_container_upload_unknown_user_filter`
how_to_implement: You must install splunk AWS add on and Splunk App for AWS. This search works with AWS CloudTrail logs.
known_false_positives: No false positives have been identified at this time.
references:
    - https://attack.mitre.org/techniques/T1204/003/
drilldown_searches:
    - name: View the detection results for - "$user$"
      search: '%original_detection_search% | search  user = "$user$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$user$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: 7d
      latest_offset: "0"
intermediate_findings:
    entities:
        - field: user
          type: user
          score: 20
          message: Container uploaded from unknown user $user$
threat_objects:
    - field: src
      type: ip_address
analytic_story:
    - Dev Sec Ops
asset_type: AWS Account
mitre_attack_id:
    - T1204.003
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: cloud
security_domain: network
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1204.003/aws_ecr_container_upload/aws_ecr_container_upload.json
          sourcetype: aws:cloudtrail
          source: aws_cloudtrail
      test_type: unit

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