ICS Fundamentals By Raed Ahsan
Supervisory Control And Data
Acquisition
SCADA systems provide high-level data management of the distributed assets in an ICS
environment.
Image credit to Infosec for providing the diagram of a SCADA System.
SCADA Systems are mostly found in power generation, water treatment plants, oil and gas
pipelines, and waste treatment systems of water.
This enables the operator to control, monitor, and take action based on the results that it gets
from the distributed assets that communicate with the SCADA system via communications
equipment in between to convert digital signals to human readable format.
The control of the distributed systems through SCADA can be fully automated or can also be set
to require human intervention.
SCADA systems can sometimes continue to operate even with one or more faults. (only in some
cases).
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ICS Fundamentals By Raed Ahsan
All the communication can either be connected wirelessly or through serial connections.
The control server is where alarms are received, system trends are analysed, and reporting is
done.
The field sites receive instructions from the control center and perform local controls of the
actuators, along with providing reports directly.
For a better understanding of the SCADA systems:
Image credit to Infosec for providing detailed categorization of the SCADA and field sites.
A device that can directly communicate with the field controllers, like RTU, PLC, or also with the
supervisory zone, is called an Intelligent Electronic Device (IED).
Intelligent Electronic Device (IED): Microprocessor-based controllers common to the electric
power industry, which operate devices such as protective relays, on-load tap changers, circuit
breakers and capacitor banks.
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ICS Fundamentals By Raed Ahsan
Image credit to infose: it shows how IED can be placed to make communication easier and
direct with the supervisory zones, or within the field controller zones to transmit the data to the
supervisory zone.
Distributed Control Systems (DCS):
Found in the petrochemical, pharmaceutical manufacturing industry, and nuclear power.
DCS doesn’t require a centralized SCADA system to operate itself (in some cases).
DCS contains the supervisory level of control to manage multiple subsystems, also called PCS -
process control systems.
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ICS Fundamentals By Raed Ahsan
The data gets stored and collected within the PCS that goes into the DCS and from there, the
DCS will either make a decision directly in an automated way, or else, transfer the data to the
SCADA zone, which will forward the commands and steps on what to do next via a
communication zone in between.
ICS Communications:
OT communications can sometimes be dependent on traditional methods like wired, serial
cables, or can even be wireless through a wifi, microwave signals, or 2G/4G radiation.
Serial communications like RS232 are only used for ongoing communications between field
devices. Also used in Field Controller Zone.
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ICS Fundamentals By Raed Ahsan
Image credit to infosec
These are the protocols that automate building automation systems.
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ICS Fundamentals By Raed Ahsan
Image Credit to Infosec
These are some of the most commonly used protocols in an OT environment to enable
communications between different sites and zones. They work together via hardware or
software to provide protocol interoperability.
ICS Supervisory Zone:
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ICS Fundamentals By Raed Ahsan
The supervisory zone is a zone where system operators are looped into a production process.
HMI, in the supervisory zone, can provide direct access to an operational process. And, it
displays information like:
● Operational Status
● Alarms and Notifications
● Machine I/O data.
In some cases, it can also be remotely controlled.
Engineering Workstations:
● Primary location plant operators work from
● Can be used as a thick-client or thin-client infrastructure
● Often allows full control of entire process operations.
Most of the time that operators spend their time is here, in the engineering workstations.
Control Server:
● Centralization of control services
● Control optimization
● System access control
● Historical data
● Device management
Is considered as a main server where all the logs, service information, process details, and
management information is stored.
There are some software consideration to keep in mind because in IT environments, we can
update/upgrade our systems any time we want, or whenever there’s an update.
But it’s not the case in OT environments.
● Requires special configurations
● Common to see deprecated devices
● Difficult or impossible to upgrade
● Upgrade or product replacements may be really expensive
It’s difficult or impossible to upgrade software in an OT environment because they are all
connected via outdated systems, and updating any one of them or even changing a single byte
can result in a complete disaster, and unless carefully analyzed before executing.
PLC uses ladder logic to create the rules from the engineering workstations and implement it
itself and the rules are created by using a set of rungs in the ladder logic.
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ICS Fundamentals By Raed Ahsan
This is how the software of PLC looks like where the lines are where you can create the rungs
and depending on the correct set of rules, the PLC will execute the program and work with the
physical objects accordingly.
Data Acquisition, management, and
business processes:
Each type of ICS rely on data to accomplish a certain task or a set of processes.
Data acquisition, management, and business processes are all an integral part of the ICS
environments where the people can manage, monitor, analyse, improve the quality, make
adjustments, and execute accordingly by keeping the business goals in mind.
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ICS Fundamentals By Raed Ahsan
Data is acquired, analysed, managed accordingly, if needed, the adjustments will be made to
fulfil the requirement of the business goals, and then execute in the business processes and
monitored continuously to ensure accuracy, security, and availability.
