A real world SCADA system can monitor and control hundreds to hundreds of thousands of I/O points. SCADA system evolve rapidly and are now penetrating the market with a number of I/O channels from 100K up to near 1 M I/O channels currently under development.
SCADA systems evolve from hardware and software in the 1970s to current system that includes standard PCs and operating systems, TCP/IP communications, and internet access. Security of control systems became a concern issue since the advent of internet and the rise of terrorist threats.
In addition, the LANs that these architectures use raise a new set of security concerns, leading to the introduction of features such as encrypted data sets and dedicated access mechanism in information assurance applications. In the following we provide a summary of the most important developments of the SCADA control systems.
In the past, control systems were isolated from other information technology (IT) systems. Connection to the internet is new (early 1990s) and debatable among specialists. Many specialists agree that exposing control systems to the internet is not good idea. However, without any connection to the internet these systems are still vulnerable to external or internal attackers that can exploit vulnerabilities in software such as operating systems, custom and vendor software, data storage software, databases, and applications.