New Public Repository Container Image detected in AWS ECR

cloudtrail

Classification:

attack

Tactic:

TA0010-exfiltration

Technique:

T1567-exfiltration-over-web-service

Goal

Detect when a new image is uploaded to the public ECR. This could be a potential exfil route of data from the cloud. Could be a supply chain effect as well if a company hosts their containers here for consumers.

NOTE: Amazon ECR requires that users have permission to make calls to the ecr-public:GetAuthorizationToken and sts:GetServiceBearerToken API through an IAM policy before they can authenticate to a registry and push any images to an Amazon ECR repository.

Strategy

Detect when @evt.name:PutImage is used against the ecr-public.amazonaws.com API.

Triage & Response

  1. Check that {{@responseElements.image.imageId.imageDigest}} is a valid sha256 hash for the container image with a tag of {{@responseElements.image.imageId.imageTag}} in the {{@responseElements.image.repositoryName}} repository on AWS Account {{@userIdentity.accountId}}.
  2. If the hash is not valid for that container image, determine if the container image was placed there for a malicious purpose.