Perhaps, the most well-known control system attack Stuxnet was a sophisticated malware attack on the uranium nuclear plant in Natanz, Iran in 2010. The worm spread into the target environment crossing the air gap, affecting the programmable logic controller (PLC) through an infected USB flash drive. Stuxnet exploited the control system's physical nature which is exactly a compromise of Iranian PLCs to gather information on industrial systems and caused the centrifuges to spin at abnormally high rates to tear themselves.
Natanz Nuclear Enrichment Facility
Stuxnet  targeted the Industrial control systems with the key intent to modify the code in PLCs to deviate their actual behavior. This deviation is noticeable only over a long period. The attack was sophisticated with great efforts that were taken to hide deviation by imitating the legitimate data through a replay attack. To succeed better, several methods such as process injection, zero-day exploits, security holes in a rootkit, network discovery, etc were used.
Know thy system under attack
Natanz nuclear plant which was attacked by Stuxnet is one of the cyber physical system. The cyber-physical system (CPS) is an electronic control system that supervises and watch continuously on the behavior of physical processes  and actuate the processes for behavioral changes so that the physical system works in a better and appropriate fashion.
CPS includes two main components
1. Physical domain consisting of Physical systems, sensors, and actuators
2. Cyber Domain comprising Control, Computation, and Communication.
The Cyber domain sense, monitor and control the physical process utilizing the smart sensor network . In simple, it can be viewed as the integration of supervising control systems, communication networks, sensors, and embedded systems. NIST  refers to CPS as the system that comprises interacting digital, analog, physical, and human components engineered for function through integrated physics and logic.
CPS are smart systems that are highly interconnected to provide new functionalities to enhance the quality of life and facilitate technological advancement in various critical infrastructures fields such as oil and gas pipelines, smart manufacturing, water management, personalized health care, smart transportation, wind farms, space stations, Air Traffic Control (ATC) system, Unmanned Aerial Vehicle (UAV) navigation system, energy infrastructure and so on.
CPS data breaches were realized in many more real time systems such as Maroochy Sewage Water Breach, Australia in 2000, and Ukraine Power grid attack in 2015. Hacks on drones, smart cars, are some of the CPS security breaches which in turn may result in loss of secret data, physical property, or human lives. The attack points of the CPS are in general the Physical system, sensors, network, and the controller
Need for Secure Cyber-Physical System
PESU C-ISFCR and C-IOT stay focussed on initiating and developing research recommendations to augment Cyber-Physical System Security. Projects on a variety of SCADA simulations are undertaken to create a SCADA testbed for Industrial IoT 4.0. These testbeds will be further utilized to perform a vulnerability assessment of the system. More research is required to implement mitigation strategies based on laws of physics supported by the concerned system to ensure a secure automated system and technology.
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