programmable automation controller (PAC)
Programmable automation controller (PAC) is a term that is loosely used to describe any type of automation controller that incorporates higher-level instructions. The systems are used in industrial control systems (ICS) for machinery in a wide range of industries, including those involved in critical infrastructure. A PAC makes it possible to provide more complex instructions to automated equipment, enabling much the same capabilities as PC-based controls in an all-in-one package like a programmable logic controller (PLC).
PLCs were created in the 1960s as an improvement over relay-based systems. Although more advanced than relay, PLCs still functioned by simple ladder logic that resembled the appearance of wiring diagrams of relay systems. In the beginning, PLCs had limited memory, required proprietary terminals and lacked remote I/O (input/output) capabilities. Additional abilities required adding hardware cards. PC-based programming of PLC was introduced in the 1980s and offered greater abilities, more memory and sequential control.
Early PACs came on the scene at the beginning of the 21st century. PACs offered a combination of the abilities and technologies of distributed control systems (DCS) and remote terminal units (RTU) as well as some of the abilities offered by PC control. PACs offered more connectivity options and broader control while maintaining smaller packaging and durability for environmental stresses and shock. With these new improvements, PACs were widely adopted. Controllers of both types (PAC and PLC) have advanced since their creation. With the increased capabilities of PLC, the differentiating lines between the two have blurred. Higher-end PLCs with increased capabilities are often marketed as PAC.
programmable logic controller (PLC)
A programmable logic controller (PLC) is a small, modular solid state computer with customized instructions for performing a particular task. PLCs, which are used in industrial control systems (ICS) for a wide variety of industries, have largely replaced mechanical relays, drum sequencers and cam timers. PLCs are useful tools for repeatable processes because they have no mechanical parts and they can gather information. Each central processor unit (CPU) continually loops through an input scan, program scan, output scan and housekeeping mode, repetitively performing a single task while monitoring conditions. The information the controller gathers can be used as feedback to guide needed changes and improvements to processes, some of which can be performed automatically according to the device’s coding.
PLCs take up less space, perform more complex tasks and are more customizable than the mechanical technologies they have replaced. They are known for their ability to operate continuously without maintenance and have had a great impact on digitizing a great many industries, particularly manufacturing. The first PLC, for example, was invented by Dick Morley in 1969 for General Motors and performed uninterrupted for 20 years before being retired. Five programming languages are used to code PLCs, as specified by International Electrotechnical Commission (IEC) 61131. They are Ladder Logic, Function Block Diagram (FBD), Structured Text (ST), Instruction List (IL) and Sequential Function Chart (SFC). Should significant code changes be required and the PLC's memory is embedded, the controller can be recoded in place. When the PLC's memory is not embedded on the circuit board and significant code changes are required, the memory can be removed from an exterior slot on the PLC and replaced without requiring the assistance of a programmer on site.
industrial control system (ICS)
Industrial control system (ICS) is a general term used to describe the integration of hardware and software with network connectivity in order to support critical infrastructure. ICS technologies include, but are not limited to, supervisory control and data acquisition (SCADA) and distributed control systems (DCS), industrial automation and control systems (IACS), programmable logic controllers (PLCs), programmable automation controllers (PACs), remote terminal units (RTUs), control servers, intelligent electronic devices (IEDs) and sensors.
Historically, most machinery and engineering components used in manufacturing and the operation of power plants, water and wastewater plants, transport industries and other critical infrastructures were dumb, and those that were computerized typically used proprietary protocols. The networks they belonged to were air-gappedand protected from the outside world. This has changed over the years and components of today's ICSs are often connected directly or indirectly to the internet.
Advances in smart sensor technology and wireless networking have made the blending of operational technology (OT) with information technology (IT) desirable and cost-effective. Despite the benefits of increased speed, better responsiveness to conditions and improved reliability that IT/OT convergence had brought, however, there are drawbacks in terms of security.
Targeted attacks against ICSs by terrorists pose a threat to most nations around the world. As remote telemetry units used to input change become more capable of local control and as the Internet of Things (IoT) and Industrial IoT continue to grow, it becomes increasingly important for strategies to protect ICSs from security threats be top of mind. In the United States, the Department of Homeland Security (DHS) has offered these recommends for protecting industrial control systems:
· Use application whitelisting to protect infrastructure from potentially harmful programming.
· Implement configuration management and patch management controls to keep control systems secure.
· Reduce attack surface areas by segmenting networks into logical parts and restricting host-to-host communications paths.
· Require multi-factor authentication and enforce the principle of least privilege (POLP).
· Require remote access to be operator controlled and time limited.
· Monitor traffic within the control network and on ICS perimeters.
· Analyze access logs and verify all anomalies.
· Ensure the restore includes golden records so systems can be rolled back to last known good state