Control Systems Security for the Energy Sector

O f today's many physical systems that impact or are impacted by networked computers, computerized control systems represent a class of applications of both great importance and national interest. A growing trend, motivated by economic and design purposes, is to embed intelligence into physical systems and connect the various systems through a common industrial control network whose dual purpose is to monitor and control the plant. These cyber-physical systems often rely on a supervisory control processor that allows operators to monitor the state of each physical device in the plant and change their operating set points. The design of protection equipment was originally based on hardware but is increasingly performed by transferring ana-log and digital values from small controllers embedded in the devices to a central plant control system, which receives sensor information and exerts commands through networks. As a result, there exists a situation in which certain commands sent over the network can manipulate physical devices. If the manipulation is done in a way that puts the cyber-physical system in an unsafe state, a simple cybercommand could result not only in damage to equipment, but also in injury or loss of life. In general, embedded systems used in industrial control networks include programmable logic controllers (PLCs), distributed control systems, and safety-instru-mented systems. In the hierarchical Sensory Control and Data Acquisition (SCADA) reference model, remote terminal units refer to the plant controllers and intelligent electronic devices refer to the controllers embedded in the machines. Due to the presence of digital controllers that can turn parts of the system on and off, it's more appropriate to refer to a hybrid physical state than to a physical state, which typically refers only to the analog portion of the system and not to the state of its switches. Most protective controls modify the system's hybrid state—often when the analog states reach some boundary conditions—and the change impacts the underlying physical laws to which the hybrid state refers. The transition from using direct serial links for each communication to using shared Ethernet media and the Internet protocol (IP) was a big leap for these systems. In the past, information networks and controls of this type were either in isolated environments—such as 3 manufacturing plants and power generation facilities— or were limited to control infrastructures such as those used for electricity transmission or gas pipelines. The operation and management of these facilities were characterized by …