T1612: Build Image on Host

Adversaries may build a container image directly on a host to bypass defenses that monitor for the retrieval of malicious images from a public registry. A remote build request may be sent to the Docker API that includes a Dockerfile that pulls a vanilla base image, such as alpine, from a public or local registry and then builds a custom image upon it.

An adversary may take advantage of that build API to build a custom image on the host that includes malware downloaded from their C2 server, and then they may utilize Deploy Container using that custom image. If the base image is pulled from a public registry, defenses will likely not detect the image as malicious since it’s a vanilla image. If the base image already resides in a local registry, the pull may be considered even less suspicious since the image is already in the environment.

Detection

IDDS0007Data source and componentImage: Image CreationDescription

Monitor for unexpected Docker image build requests to the Docker daemon on hosts in the environment.

IDDS0029Data source and componentNetwork Traffic: Network Connection CreationDescription

Monitor for established network communications with anomalous IPs that have never been seen before in the environment that may indicate the download of malicious code.

IDDS0029Data source and componentNetwork Traffic: Network Traffic ContentDescription

Monitor for network traffic associated with requests and/or downloads of container images, especially those that may be anomalous or known malicious.

IDDS0029Data source and componentNetwork Traffic: Network Traffic FlowDescription

Monitor for established network communications with anomalous IPs that have never been seen before in the environment that may indicate the download of malicious code.

Mitigation

IDM1035NameLimit Access to Resource Over NetworkDescription

Limit communications with the container service to local Unix sockets or remote access via SSH. Require secure port access to communicate with the APIs over TLS by disabling unauthenticated access to the Docker API on port 2375. Instead, communicate with the Docker API over TLS on port 2376.

IDM1026NamePrivileged Account ManagementDescription

Ensure containers are not running as root by default. In Kubernetes environments, consider defining Pod Security Standards that prevent pods from running privileged containers.

IDM1030NameNetwork SegmentationDescription

Deny direct remote access to internal systems through the use of network proxies, gateways, and firewalls.

IDM1047NameAuditDescription

Audit images deployed within the environment to ensure they do not contain any malicious components.