T1611: Escape to Host

Adversaries may break out of a container to gain access to the underlying host. This can allow an adversary access to other containerized resources from the host level or to the host itself. In principle, containerized resources should provide a clear separation of application functionality and be isolated from the host environment.

There are multiple ways an adversary may escape to a host environment. Examples include creating a container configured to mount the host’s filesystem using the bind parameter, which allows the adversary to drop payloads and execute control utilities such as cron on the host; utilizing a privileged container to run commands or load a malicious kernel module on the underlying host; or abusing system calls such as unshare and keyctl to escalate privileges and steal secrets.

Additionally, an adversary may be able to exploit a compromised container with a mounted container management socket, such as docker.sock, to break out of the container via a Container Administration Command. Adversaries may also escape via Exploitation for Privilege Escalation, such as exploiting vulnerabilities in global symbolic links in order to access the root directory of a host machine.

Gaining access to the host may provide the adversary with the opportunity to achieve follow-on objectives, such as establishing persistence, moving laterally within the environment, accessing other containers running on the host, or setting up a command and control channel on the host.

Detection

IDDS0008Data source and componentKernel: Kernel Module LoadDescription

Monitor for the installation of kernel modules that could be abused to escape containers on a host.

IDDS0034Data source and componentVolume: Volume ModificationDescription

Monitor cluster-level (Kubernetes) data and events associated with changing containers' volume configurations.

IDDS0032Data source and componentContainer: Container CreationDescription

Monitor for the deployment of suspicious or unknown container images and pods in your environment, particularly containers running as root.

IDDS0009Data source and componentProcess: Process CreationDescription

Monitor for process activity (such as unexpected processes spawning outside a container and/or on a host) that might indicate an attempt to escape from a privileged container to host.

IDDS0009Data source and componentProcess: OS API ExecutionDescription

Monitor for unexpected usage of syscalls such as mount that may indicate an attempt to escape from a privileged container to host.

Mitigation

IDM1042NameDisable or Remove Feature or ProgramDescription

Remove unnecessary tools and software from containers.

IDM1038NameExecution PreventionDescription

Use read-only containers, read-only file systems, and minimal images when possible to prevent the running of commands. Where possible, also consider using application control and software restriction tools (such as those provided by SELinux) to restrict access to files, processes, and system calls in containers.

IDM1048NameApplication Isolation and SandboxingDescription

Consider utilizing seccomp, seccomp-bpf, or a similar solution that restricts certain system calls such as mount. In Kubernetes environments, consider defining Pod Security Standards that limit container access to host process namespaces, the host network, and the host file system.

IDM1026NamePrivileged Account ManagementDescription

Ensure containers are not running as root by default and do not use unnecessary privileges or mounted components. In Kubernetes environments, consider defining Pod Security Standards that prevent pods from running privileged containers.