Adversaries may cause a denial of control to temporarily prevent operators and engineers from interacting with process controls. An adversary may attempt to deny process control access to cause a temporary loss of communication with the control device or to prevent operator adjustment of process controls. An affected process may still be operating during the period of control loss, but not necessarily in a desired state.    In the Maroochy attack, the adversary was able to temporarily shut an investigator out of the network preventing them from issuing any controls. In the 2017 Dallas Siren incident operators were unable to disable the false alarms from the Office of Emergency Management headquarters. 
Take and store data backups from end user systems and critical servers. Ensure backup and storage systems are hardened and kept separate from the corporate network to prevent compromise. Maintain and exercise incident response plans , including the management of \gold-copy\ back-up images and configurations for key systems to enable quick recovery and response from adversarial activities that impact control, view, or availability.
|M0810||Out-of-Band Communications Channel||
Provide operators with redundant, out-of-band communication to support monitoring and control of the operational processes, especially when recovering from a network outage . Out-of-band communication should utilize diverse systems and technologies to minimize common failure modes and vulnerabilities within the communications infrastructure. For example, wireless networks (e.g., 3G, 4G) can be used to provide diverse and redundant delivery of data.
|M0811||Redundancy of Service||
Hot-standbys in diverse locations can ensure continued operations if the primarily system are compromised or unavailable. At the network layer, protocols such as the Parallel Redundancy Protocol can be used to simultaneously use redundant and diverse communication over a local network.