Security system, device, and method for operational technology networks

A protection system, method, and a security device can protect an operational technology (OT) system having connected hardware equipment, including at least an interface that can receive a control communication and an industrial control device (ICD) for controlling at least one industrial device. They feature tasks/steps that receive control communication from the communication interface, determine whether the received control communication contains an undesirable control command, and either pass or block the received control communication to the ICD depending on whether the received control communication contains an undesirable control command. The security device can be disposed between a source of communication in an OT network and the ICD for protection.