Aerospace and Electronic Systems Magazine May 2017 - 28

Feature Article:

DOI. No. 10.1109/MAES.2017.160047

Security of SCADA Systems Against Cyber-Physical Attacks
Van Long Do, Viettel Research and Development Institute, Hanoi, Vietnam; Lionel Fillatre,
Université Côte d'Azur, Sophia Antipolis, France; Igor Nikiforov, Université de Technologie
de Troyes, Troyes, France, Peter Willett, University of Connecticut, Storrs, CT, USA

INTRODUCTION
Supervisory control and data acquisition (SCADA) systems are
highly distributed systems used to control and monitor geographically dispersed assets-often scattered over thousands of square kilometers-in which centralized data acquisition is critical to system
operation [1]. These large-scale industrial control systems (ICSs)
have been playing an extremely important role in most safety-critical infrastructures [2], such as electric power grids, transportation
systems, communication networks, oil and gas pipelines, water distribution and irrigation networks, and multiple facilities including
heating, ventilation and air conditioning systems for buildings, and
traffic control systems for airports-the list is long. These safetycritical assets, however, are becoming increasingly susceptible to
cyber-physical attacks1 on both physical and cyber layers [3].

SCADA ARCHITECTURE
The typical architecture of a modern SCADA system, as shown in
Figure 1, consists of three layers: the supervisory control layer, the
automatic control layer, and the physical layer. The exchange of
data among entities in the system is carried out through the communication network [4].

Supervisory Control Layer
The supervisory control layer (or the control center) is responsible for
monitoring the operation of SCADA systems by gathering data from
1

In this manuscript, we use the term cyber-physical attack instead of cyber attack to describe the coordination of both cyber
and physical activities in a malicious attack.

Authors' current addresses: V. L. Do, Viettel Research and Development Institute, Viettel Building B1, Lot 1, Hoa Lac Hitech
Park - Thach That, Hanoi, Vietnam; L. Fillatre, Université Côte
d'Azur, CNRS, I3S - CS 40121 - 06903 Sophia Antipolis CEDEX, France; I. Nikiforov, Université de Technologie de Troyes,
UTT/ICD/LM2S, UMR 6281, CNRS, 12, rue Marie Curie, CS
42060 Troyes Cedex, 10004 France, E-mail: (nikiforov@utt.fr).
P. Willett, University of Connecticut, ECE Department, 371
Fairfield Road, U-4157, Storrs, CT 06269-4157, USA.
Manuscript received February 24, 2016, revised July 2, 2016,
and ready for publication August 2, 2016.
Review handled by H. Liu.
0885/8985/17/$26.00 © 2017 IEEE
28

field devices, performing control and supervisory tasks, and sending
control commands to field controllers through the communication
network. The control center of a typical SCADA system consists of
following elements: the SCADA server, the builder server, the communication server, the database server, the diagnostic server, the application server, the human-machine interface, and the system operators. For example, the database server stores all process information,
which can be used for data analysis, ranging from process control
analysis right up to the level of the company's business plan.

Automatic Control Layer
The automatic control layer (or regulatory control layer) is in charge
of regulating the operation of physical processes based on control
commands from the control center and sensor measurements from
field devices. The control signals are then transmitted to field devices through the communication network. Various system variables,
including control commands, sensor measurements, and control signals, are gathered within the control center for supervisory and management purposes. In this layer, principal elements include master
terminal units (MTUs), remote terminal units (RTUs), programmable logic controllers (PLCs), and intelligent electronic devices [1].

Physical Layer
The physical processes (e.g., electric power grids, gas pipelines,
and water networks) are equipped with actuators (e.g., motors,
compressors, pumps, and valves), sensors (e.g., temperature sensors, pressure sensors, flow sensors, level sensors, and speed sensors), and protection devices (e.g., circuit breakers and protective
relays) to realize technological goals. The physical elements are
controlled and monitored by the control center through the automatic control layer and the communication network.

Communication Network
Because of their geographic dispersal, modern SCADA systems
depend heavily on their communication network for exchanging
information (e.g., command signals, control signals, and sensor
readings) between the control center and the field devices. The
SCADA communication network can be broadly classified as a
corporate, process, field, or vendor network [1]. The evolution of
communication technology [4] has made modern SCADA systems
vulnerable to cyber attacks. For example, powerful attackers may

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