In an environment such as a cloud computing environment where various guests can be provisioned on a host machine or other hardware device, it can be desirable to prevent those users from rebooting or otherwise restarting the machine or other resources using unauthorized information or images that can be obtained from across the network. A cloud manager can cause one or more network switches or other routing or communication processing components to deny communication access between user-accessible ports on a machine or device and the provisioning systems, or other specific network resources, such that the user cannot cause the host machine to pull information from those resources upon a restart or reboot of the machine. Further, various actions can be taken upon a reboot or attempted reboot, such as to isolate the host machine or even power off the specific machine.