  Industrial Control System (ICS) is a general term that includes supervisory
control & data acquisition (SCADA) systems, distributed control systems (DCS),
and other control system configurations such as programmable logic controllers
(PLC). ICSs are often found in the industrial sectors and critical
infrastructures, such as nuclear and thermal plants, water treatment
facilities, power generation, heavy industries, and distribution systems.
Though ICSs were kept isolated from the Internet for so long, significant
achievable business benefits are driving a convergence between ICSs and the
Internet as well as information technology (IT) environments, such as cloud
computing. As a result, ICSs have been exposed to the attack vectors used in
the majority of cyber-attacks. However, ICS devices are inherently much less
secure against such advanced attack scenarios. A compromise to ICS can lead to
enormous physical damage and danger to human lives. In this work, we have a
close look at the shift of the ICS from stand-alone systems to cloud-based
environments. Then we discuss the major works, from industry and academia
towards the development of the secure ICSs, especially applicability of the
machine learning techniques for the ICS cyber-security. The work may help to
address the challenges of securing industrial processes, particularly while
migrating them to the cloud environments.
