The rule 'GCP K8s Pod Using Host PID Namespace' detects the creation or modification of pods in Google Cloud Platform's Kubernetes that utilize the host PID namespace. This setting allows containers within a pod to directly access and view the host's process list, potentially providing an escape route to the underlying host system. Such configurations can be a security concern as they may allow for unintended interactions with the host's processes and resources. Consequently, this rule aims to flag any instances where pods are created or modified with host PID enabled, allowing for proactive investigation and remediation. The rule is considered to have a medium severity as it addresses significant security risks inherent to container orchestration environments, particularly Kubernetes deployments. The runbook suggests investigating the necessity of using the host PID namespace and creating a support ticket for further actions if warranted.