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.
Open detection, hunting, mitigation, and evidence workspace
Detection logic
Monitor for unexpected Docker image build requests to the Docker daemon on hosts in the environment. Additionally monitor for subsequent network communication with anomalous IPs that have never been seen before in the environment that indicate the download of malicious code.