SCADA FundamentalsA brief Review

M Suresh

Chief Research Engineer

Fluid Control Research Institute

www.fcriindia.com

SCADA Terminology

SUPERVISORY CONTROL AND DATA

ACQUISITION

• an industrial control system: a computer system

monitoring and controlling a process. The process

can be industrial, infrastructure or facility-based.

• Processes run in continuous, batch, repetitive, or

discrete modes

Industrial processes

• manufacturing,

• production,

• power generation,

• fabrication,

• refining

Infrastructure processes

• water treatment and distribution,

• sewage collection and treatment,

• oil and gas pipelines,

• electrical power transmission and distribution

• Wind Farms,

• Railways,

• large communication systems.

Facility processes

• Buildings (Energy, Visitor, Parking, Infra.)

• Airports (Baggage, flight scheduling, Information

displays, messaging, security,..)

• Ships (inventory, operations, services, personnel..)

• space stations (basic operations, schedule,... )

Common: They monitor and control HVAC, access, and

energy consumption

Fundamental function: SCADA

• refers to centralized systems that monitor,

control entire sites, complexes of systems

spread out over large areas

• Most control actions are performed automatically

by RTUs or PLCs.

• Host control functions are usually restricted to

basic overriding or supervisory level

intervention.

Typical SCADA operation• a PLC may control flow of cooling water through

part of an industrial process,

• SCADA HMI system allows operators to change

set points for flow,

• enable alarm conditions, such as loss of flow or

high temperature to be displayed and recorded.

• feedback control loop passes through RTU or PLC

• SCADA system monitors overall loop performance

Fundamental function: SCADA

• Data read by RTU / PLC; includes meter readings,

equipment status, etc.

• data are communicated to SCADA as required.

• Data is compiled, formatted on HMI for control room

operator to make supervisory decisions to adjust or

override normal RTU /PLC controls.

• Data may also be fed to Historian (a Database

Management System), to allow trending, other

analytical auditing

SCADA system componentsSupervisory (computer) system

• acquires data on process, sends commands (control) to

process.

Remote Terminal Units (RTU)

• connects to sensors in the process, digitises data

• sends digital data to supervisory system.

Programmable Logic Controller (PLC)

• field devices typically more economical, versatile, flexible,

configurable than RTUs.

Communication / Telemetry

• infrastructure connecting supervisory system to RTU.

Human-Machine Interface (HMI)

• apparatus that presents process data to human operator,

• human operator monitors and controls the process.

Generally Said, Elements of SCADA

• Sensors and actuators

• RTUs/PLCs

• Communication

• MTU

• Front End Processor

• SCADA server

• Historical/Redundant/Safety Server

• HMI computer

• HMI software

Lets go into details..

Levels in SCADA

Level 4: Enterprise

� Corporate LAN/WAN

� World Wide Web

� Virtual Private Network

� Firewall for remote

users

Level 2: Telemetry

� Fiber

� Radio

� Telephone leased line

� Protocols

Level 1: Field

� Devices

� RTUs / PLCs

� Sensors

Level 3: SCADA - MTU

� Operator

Workstations

� Control

� Engineering

Workstations

� Servers – Data

logging

Supervisory Station

(Master Terminal System)

• Computer / servers and software responsible for

communicating with field equipment and HMI

software.

• master station may be a single PC.

• master station may include multiple servers,

distributed software applications, and disaster

recovery sites.

• hot-standby dual-redundancy possible at

present for continuous control and monitoring.

Remote Terminal Unit

• microprocessor controlled electronic device that

interfaces to signals from sensors in physical

world.

• Transmits data to remotely located Supervisory

system and/or alters state of connected field

objects based on control messages received.

• Monitors field digital, analog parameters

• Outputs signals to actuators for local control

• RTU interfaces to Supervisory Station with

different communication media

Programmable Logic Controller

• a digital computer used for automation of

electromechanical processes, eg. control of

machinery on factory assembly lines, amusement

rides, etc.

• designed for multiple inputs and output

arrangements,

• Designed for extended temperature ranges,

immunity to electrical noise, resistance to vibration

and impact.

• Programs to control machine operation stored in

battery-backed or non-volatile memory

PLC

• Early PLCs were

designed to replace

relay logic systems.

• These PLCs were

programmed in ladder

logic, strongly

resembles schematic

diagram of relay logic.

• Proprietary special-

purpose programming

terminals had dedicated

function keys

representing various

logical elements of PLC

programs.

Signal Flow in PLC

I:0/6

I:1/4

O:0/7

O:1/5

I:0/6 O:0/7

I:1/4 O:1/5Ladder

Program

Data Output

Image

Table

Input

Image

Table

Processor MemoryInput Module

Input Devices

I:0/6

I:1/4

Output Module

Output Devices

Programming System

O:0/7

O:1/5

Typical PLC and SCADA link

Programmable automation controller

• compact controller combines features

and capabilities of a PC-based Data

Acquisition System with that of

PLC/RTU.

• PACs used in industrial settings for

process control, data acquisition, remote

equipment monitoring, machine vision,

and motion control.

• communicate over networks; support

protocols TCP/IP, OPC, etc.

• PACs assist data transfer from

machines they control to other machines

or to application software and databases

Intelligent Electronic Device (IED)

Ethernet with DNP3, IEC 61850, MODBUS

IEC 61131-3

• defines five programming languages for

programmable control systems:

• LD Ladder diagram

• IL Instruction list

• FBD Function block diagram

• ST Structured text

• SFC Sequential function chart IEC 848

http://www.en.omesim.com

RTU vs PLC • RTUs focus on remote monitoring and control.

• RTUs have high demand for application, communications

and protocol flexibility.

• PLCs designed around localized fast control of discrete

variables and analog inputs.

• RTUs built with RTOS benefit from faster task processing,

reduced memory requirements, and lower risk of failure due

to overly complex code.

• PLCs have proprietary OS

• RTUs have Communication Protocol Supports for TCP/IP,

Mobile/portable two-way radio, Analog/digital trunking ,

broadband (e.g. WLAN), Cellular modem (GPRS), etc.

RTU vs PLC • Generally RTUs can handle more number of PID

loops than PLCs for same costs.

• SOE (Sequence of Events recording) is generally

lacking in PLCs.

• RTUs can log thousands of events, time tagged to

1ms.

• PLCs lack Data logging features.

• RTUs have High storage capacity (FLASH, DRAM,

SRAM) for adding programs, functions and data

storage.

RTU high-end capabilities

• Support for multiple passwords at multiple abstraction levels – Allows for compartmentalization of application software and SCADA hardware access control

• Hardware IP firewalls

• Support for Data Encryption Standard (DES) and Advanced Encryption Standard (AES)

• Adding authorization to security routines

• Maintaining a sign-in and activity log

• Remote “safe” download of firmware, applications, enabling rapid, secure configuration and upgrades of software code

RTU-Server Data Communication

HMI Operator

Terminals

Sizes typically 4”, 6”, 10”, 15”, 17”.

SIEMENS, Schneider, Hitachi,

Mitsubishi, Advantech, Adlink, ….

• Where localised Operator Interface is needed.

• Can eliminate SCADA for minor applications

HMI Operator Terminals

• Wide variety of

ports;

• Speaker, mic

• alarm contacts,

DIO for external

(remote),

• USB, Ethernet,

RS485/232/422

• Compact flash,

SDCard

HMI Operator Terminals

Programming Software

Configuration Tools

PLC Configuration and programming

HMI Panel Programming software

• Eg. STEP7, Vijeo, etc.

• Permits designing screens for Operator, Alarms,

Graphic plots, Mimics, keys and buttons,..

• Program the Function keys, Security, etc.

• Configuration of Ports, MODBUS register access, PLC

link, ..

HMI Panel Programming software

HMI or MMI Software

• links to SCADA databases and software

programs

• provides trending, diagnostic data, and

management information such as scheduled

maintenance procedures, logistic information,

detailed schematics for a particular sensor or

machine, and expert-system troubleshooting

guides.

HMI mimic• Presents information to operators graphically, in

the form of mimic diagram.

• See schematic representation of plant being

controlled.

• Mimic diagrams may consist of line graphics and

schematic symbols to represent process elements,

• may consist of digital photographs of process

equipment overlain with animated symbols

Alarm handling

• SCADA monitors whether certain alarm conditions

are satisfied to determine occurrence of alarm

events

• Once an alarm event is detected, one or more

actions are taken

• activation of one or more alarm indicators,

• generation of email or text messages

Alarm handling

• An operator may have to acknowledge alarm event;

• this may deactivate some alarm indicators,

• other indicators may remain active until alarm

conditions clear.

• Explicit Alarms: NORMAL or ALARM based on

analog and digital points

• Implicit Alarms: analog point within or outside limit

values

Data Communication• Twisted-Pair Metallic Cable (STP)

• Coaxial Metallic Cable (Co-ax)

• Fiber Optic Cable (FOC)

• Power Line Carrier (PLCC)

• Very Small Aperture Terminal (VSAT: Ku, C)

• Leased Telephone Lines (LTN, PSTN)

• Very High Frequency Radio (VHF)

• Ultra High Frequency Radio (UHF)

• Microwave Radio (MW)

IEEE Standards in SCADA

• IEEE Std 999-1992 – IEEE Recommended Practice for Master/Remote Supervisory Control and Data Acquisition (SCADA) Communications.

• applies to use of serial digital transmissions SCADA systems having geographically dispersed terminals.

• IEEE Std 1379-2000 – IEEE Recommended Practice for Data Communications Between Remote Terminal Units and Intelligent Electronic Devices in a Substation.

• uniform set of guidelines for communications and interoperation of IEDs and RTUs in an electric utility substation.

IEC 60870-5IEC 60870-5-1 (1990-02) • Specifies basic requirements for services to be provided by the data link

and physical layers for telecontrol applications. IEC-60870-5-2 (1992-04) • selection of link transmission procedures using a control field and

optional address field; IEC 60870-5-3 (1992-09) • specifies rules for structuring application data units in transmission

frames of telecontrol systems; general structure of application data and basic rules to specify application data units without specifying details about information fields and their contents.

IEC 60870-5-4 (1993-08) • rules for defining information data elements and a common set of

information elements, particularly digital and analog process variables that are frequently used in telecontrol applications.

IEC 60870-5-5 (1995-06) • defines basic application functions that perform standard procedures for

telecontrol systems,

SCADA Software

• Basic SCADA functionality

• MMI (Graphical User Interface)

• Alarm Handling

• Historical Trending

• Access Control

• Data Acquisition, Automation, Display

• Archiving, Report Generation

• Interfaces to Hardware, Software

• Flexible and open architecture

• Development Tools

Supervisory Control and Data Acquisition

Supervisory Control And Data Acquisition

MIMIC Display Alarms and events

Trends and history

Alarm Handling • Based on limit and status checking

• Also expressions from derived parameters

• Alarms are time stamped and logically

centralised

• Notifications (audible, visual, Email, GSM, . . . )

• Multiple alarm priority levels

• Grouping of alarms, handling of groups

• Suppression and masking of alarms either

individually or in groups

• Filtering of alarms possible

Trending

• Multiple trending charts

• Charts are pre-defined or configured on-line

• Charts contain multiple pens,

• Zooming, scrolling, panning, ‘Hairline’

• Real-time and historical trending

Access Control

Automation of Process

• Actions can be initiated automatically triggered by

an event

• Recipes

• Sequencing and scripting possibilities

• Users organised in groups with a set of allocated

privileges

• Large number of groups possible

• Privileges limit write access to process parameters

• Some allow access to graphics and functionality to

be limited

• Reports, SQL type queries to the RTDB or logs

• Automatic generation, printing, archiving of

reports

• Use of ‘components’ for report generation

Logging and Archiving

• Data stored in compressed and proprietary format

• Logging / Archiving either for a set number of

parameters or for a set period of time

• Logging / Archiving can be frequency or event driven

• Logging of user actions together with a user ID

• VCR facility for playback of stored data

Report Generation

SCADA Software Architecture

Tren-

ding

Alarm

Display

Log

Display

Active X

Controls

Active X

Container

SCADA Client

Recipe

DB

Recipe

Managt

Ref.

DB

Alarm Log ArchiveReport

Gener.

Log DB Archive DBSQL Alarm DB

RT & Event Manager

Data

Proces

SCADA Server

RT

DB

ODBC

DDE

API/DLL

Private

ApplicationEXCEL Driver

PLC PLC

OPC

Graphics

Editor MMI

Driver

Toolkit

Project

Editor

Export

/

ImportCommercial

DB

Commercial

Devel.

tool

ASCII

Files

ASCII

File

Editor

SC

AD

A D

ev

elo

pm

en

t En

viro

nm

en

t.

Library

Data

R/W

VME

Client / Server - Publish / Subscribe - TCP/ IP

SCADA Software features

• Builder and run-time

• PLC drivers & OPC client support

• Remote monitoring by Web browser

• Comprehensive graphical components

• Windows ODBC/SQL database support

• Data log, alarm, security

• scripting

• Diagnostic tools for quick check

Development Tools

• Project editor

• Graphics editor

• Configuration through parameter

templates

• Scripting language

• Driver Development Tool Kit

SCADA Clients

SCADA Client applications

• Security of web clients is controlled by web

server’s firewall and encrypted password

protection technologies to ensure secure

operation.

• Access to web clients are controlled or denied

based on windows user name and password, or

when the number of web clients available has

been exceeded.

• Additionally, project configuration requires a local

user name, password.

SCADA Client applications

• to view any screen and read / write any variable

controlled through SCADA system.

• View-only Client is able to view information within

SCADA but unable to write to any variable or

execute code to communicate with another server.

• View-only Client used for upper management,

process optimization or causal users of control

system.

• Read only access is also available via Control

Client when access rights level is low.

SCADA Client applications

• Within control room it is typical to install client

application

• web clients allow users outside control room to

access control system data in real time.

• web client is full functional client with identical

interface to dedicated Control Clients

ALARMS

SCADA

Alarms and Alarm Management

• Purpose of Alarms

• Types of Alarms

• Alarm management issues in DCS &

SCADA

• Management of Alarms

Alarms

• draw attention of operators to condition

outside of desired normal operation.

• Such conditions require some decision or

intervention by persons.

• Alarms support operation of industrial

plants by alerting operators to a variety of

conditions.

Alarm Types / Sources

• Discrete alarms: Monitor device failures, intrusion

alarms, beacons, and flood and fire detectors.

• Analog alarm inputs: Monitor voltage, temperature,

humidity and pressure.

• Control relays: Operate remote site equipment

directly from your RTU.

• Terminal server functions: Control switches and

other devices remotely via Telnet over LAN.

• Ping alarms: Detect IP device failures and offlines

Alarm indicators and annunciation

• integral part of the human interface to the production

process

• annunciator window in a hardwired panel or a color-

coded faceplate

• message line on a control room VDU/HMI.

• Audible alarm tones or sirens

• Transmitted to remote mobile receivers (Pager, SMS,

email, etc.)

Process Alarms

• majority of alarms in process control system aid

operators to keep manufacturing process

running in the intended manner

• help achieve best possible production

performance.

• Many alarms will warn of deviations that are

linked to possible hazards

Process Alarms

• Is plant operation happening correctly?

• Process parameters within the range?

• Level, flow, pressure, temperature within

limits?

• Relates to efficiency of process or indicate

deviations from intent.

System Alarms

(Machinery or equipment alarms)

• lot of process equipment and operating devices

• System needs to work correctly 24x7

• The paranoia: everything that can possibly go

wrong will, someday!

• Our need for accurate information on health of

every element of the system

• Generally: status (eg. Bearing temperature High)

System Alarms

• Power supplies: commercial AC power, battery,

backup generators, UPS systems, etc.

• Building and facility alarms: intrusion, entry, open-

door, fire, smoke, flooding, etc.

• Environmental conditions: temperature, humidity

• RTU/communication equipment: switches,

Routers, fiber optic equipment, microwave radios,

modem.

Hazop Alarms

• A Prevention layers to prevent occurrence of

hazardous.

• Prevention layers:

– Plant Design, Process Control system, Alarms

Systems, mechanical safety devices, Interlocks,

Shutdown (SIS) systems.

• Hazops dictate large no. of ‘add-in’ alarms as ‘quick

fix’ solution to numerous operability problems.

Shutdown (or ESD) alarm

• Informs operator on initiation of SIS automatic

shutdown event.

• Basically monitor SIS.

• support corrective, subsequent actions by

operator.

• trigger for a mitigation action such as closure of

other parts of plant, isolation of fuel supplies, etc.

Fire and gas alarms

• Alarms usually built within dedicated and entirely

independent fire and gas detection systems.

• essential for protection of personnel

• assumed that all other control systems may be

shutdown or damaged due to fire or gas

conditions.

Alarm Management Issues

• Most alarms installed to deal with detailed, localized

problems of process or equipment control.

• backlog of standing alarms

• frequent minor alarms from process conditions running in

and out of limits at short intervals.

• Overloading operator with useless information at time of

crisis; nuisance in times of steady operation

• When major upset occurs, numerous alarms; as disturbance

takes hold.

Alarm Management System

• software-driven resources within DCS or SCADA

• serves to group, rationalize, prioritize the alarms

• assist operators to pack away less important

alarms whilst ensuring they do not get lost

• Tools to assist in tuning, adjustment of alarms

• Alarm log and selected history files

• Sequence of event recording

Key design principles for alarms

• Judicious use of HMI for Screen data, Graphics

• Present only relevant, useful alarms to operator

• Each alarm should have a defined response from

the operator

• Allow adequate time for an operator to respond to

an alarm

• Establish, enforce an alarm priority structure

Alarm formats

• Detailed alarm descriptions

• Alarm sorting and categorizing

• Separate Standing Alarm and Change of State

(COS) Alarm lists

• 24x7 unmanned remote alarms:

pager, SMS, email notification

Open Data Base

Connectivity

SCADA

Open Data Base Connectivity

• a standard software interface for accessing

DBMS; developed by SQL Access group in 1992.

• Helps interface SCADA/DCS software to third-

party database management software (DBMS).

• Channels SQL statements /function calls to

DBMS for data update / retrieval.

• Helps in trend plots, historical database review,

assessment, reporting, documentation.

ODBC Architecture

• Application

• Driver Manager

• Driver

• Data Source

ODBC Architecture

• Application

Performs processing and calls ODBC functions

to submit SQL statements and retrieve results.

• Driver Manager

Loads and unloads drivers on behalf of an

application.

Processes ODBC function calls or passes them

to a driver.

ODBC Architecture• Driver: Processes ODBC function calls, submits SQL

requests to a specific data source, and returns results to

application.

Can modify an application's request so that it conforms

to syntax supported by DBMS package.

• Data Source:

• data that user wants to access,

• DBMS,

• OS and network platform (if any) used to access DBMS.

ODBC Driver

• Primarily intended for reporting, it enables an

ODBC-compliant application to access from

SCADA/DCS database,

• Data: history, event, point parameter values.

• Server database queried using SQL

commands from ODBC client applications.

• custom applications written in Visual Basic or

C++ to access the server database

OLE for

Process Control

(OPC)

Object Linking and Embedding

• COM/DCOM, OLE technologies developed by

Microsoft for Windows

• a standard set of objects, interfaces and methods

for data exchange between applications

• OPC Foundation started in 1994

• most common OPC specification is OPC Data

Access.

OLE: Object Linking and Embedding

• OLE is just the

technology

which allows an

object (such as a

spreadsheet) to

be embedded

(and linked)

inside of another

document (a

word processor

document).

• Version 1 used DDE to communicate

between applications.

• Version 2 uses COM instead of DDE

OLE: Object Linking and Embedding

• Microsoft technology.

• COM is the protocol which allows OLE to work

– Rules of the road for programs to talk with each

other

– Foundation of automation

� Non-proprietary technical specification, but

copyrighted by the OPC Foundation

� Set of standards maintained by ‘OPC Foundation’,

and based on Microsoft :

� OLE (Object Linking and Embedding) / now ActiveX

� COM (component object model)

� DCOM (distributed component object model)

technologies

OPC (OLE for Process Control)

Why OPC?

• Traditionally, any time a package needs

access to data from a device, a custom

interface, or driver, had to be written.

• OPC defines common interface that is

written once, reused by any SCADA, HMI,

business or custom software packages.

• Client Server approach

Why is OPC Data Access

needed?

Software

Driver

Software

Driver

Software

Driver

Software

Driver

Display

Application

Trend

Application

Report

Application

Why OPC ?

Software

Driver

Software

Driver

Software

Driver

Software

Driver

OPC OPC OPC OPC

Display

Application

Trend

Application

Report

Application

OPC OPC OPC

Architecture

Process

I / O

Comm Protocol

Comm Interface

OPC Server

DA/AE/HDA/DX

Protocol Driver

Comm Interface

Controller

Smart Device

DCS Sub-System

Computer

Process

I / O

Comm Protocol

Comm Interface

DX

OPC DA Clients

RealTime PV

OPC AE Clients

Alarm/Event SP

OPC HDA Clients

Historian DB

OPC Server

DA/AE/HDA/DX

Protocol Driver

Comm InterfaceHDA

AE

DA

HDA

AE

DA

OPC Unified Architecture Specification

• Concepts, Security,

• Address Space, Services

• Information Model, Mappings, Profiles

• Data Access,

• Alarms and Conditions,

• Programs,

• Historical Access, etc.

http://www.opcfoundation.org

Data Access Mechanism

Commn.Bus

Data Server

Alarm ServerEthernet

Firewall

Firewall

Client

Security Issues!!

PLC/SCADA

Hacking the SCADA

• Trojan program inserted into SCADA caused

a massive natural gas explosion along the

Trans-Siberian pipeline in 1982.

• A newspaper reported the resulting fireball

yielded “the most monumental non-nuclear

explosion and fire ever seen from space.

• http://pipelineandgasjournal.com/hacking-

industrial-scada-network (November 2009

Vol. 236 No. 11)

Hacking:Sending spoofed commands to PLC

• “So you can have the operator seeing something entirely different than what's happening in the process, causing the pipe to burst and the tank to overflow”

• http://www.securityweek.com/black-hat-researchers-remotely-hack-scada-systems-oil-rigs

• Use of Firewalls: Ethernet In and Ethernet Out ports between SCADA device and Internet

SCADA Failures

Iran used SIEMENS WinCC SCADA to control centrifuges for refining uranium. Weaknesses in

WINCC combined with vulnerabilities in Microsoft's Windows OS -- allowed malworm

Stuxnet to disrupt the centrifuges; an act of sabotage (U.S. and Israel)

http://www.infoworld.com/d/security/siemens-industrial-software-targeted-stuxnet-still-full-of-holes-

206654

SCADA Security Attacks

• Denial of Service

• Plant a Trojan, virus/malware

• Delete System Files, Low level format of drives

• Take Control of SCADA System

• Info Mining (Log Keystrokes, Usernames,

Passwords, Setpoints, any Operation Info)

• Info tampering (Change Data Points, Setpoint)

Malware, Trojan

• Generally, affects Microsoft Windows OS where

SCADA is installed.

• malware spreads via mobile data carriers, USB

sticks and networks.

• Trojans activated by viewing contents of USB stick.

• Also affects PACs, Embedded systems

• Other computers

– Infrastructure computers (file servers, domain

controllers, other servers...)

– Computers with and without WinCC installed

– Virtual machines (e.g. VMWARE installations)

SCADA Security Attacks• Modify Data points on SCADA graphics to

deceive Operators that system is out of control and that ESD is essential.

• Capture, Modify, or Delete Data Logged in Operational Database SQL Server, PI Historian

• Locate Maintenance Database and modify or delete information regarding calibration and reliability tests for industrial equipment

• Use SCADA Server as a launching point to defame and compromise other system components within corporate network. (IP Spoofing)

Purposes of Attacks

• Operational or Corporate data for personal gain

or sell to competition or hold as ransom

• Gain Info for future attacks or satisfy curiosity

• Gain control of SCADA System

• to impact damage on industrial systems,

• possibly causing environmental impact,

• damage corporate identity thru public exposure

• Cause danger to facility or company by staging

a false alarm shutdown of the plant or facility

Security Issues & Potential

Consequences• Render Control Inoperative

• Render View-Access Inoperative

• Cause Non-Operation, Mis-Operation, or Mal-

Operation

• Production Loss

• Equipment Damage

• Personal Injury

• Death

Ring of Defences

Defence mechanisms

• SCADA Firewalls:

• additional layer to mediate traffic between protected network & external network.

• protect passwords, IP addresses, files, etc.

• SCADA Internal Network Design

• with own IP segment, use smart switches and proper sub-masking

• Operating systems

• with proper patches

• default NULL NT accounts and administrator accounts to be removed or renamed.

Segregation of Plant, SCADA

networks

• plant control rooms sometimes have

corporate computers with Internet and email

• Trojans, viruses can be planted through email

opened by another computer, and then

silently copied over to adjacent SCADA

servers

Batch Control issues!

• The Electronic Signature means that operations

cannot be performed until enabled by previously

assigned Windows users/user groups. Users/user

groups are assigned to the operations in the

respective application.

• Eg. SIMATIC BATCH has e-signature

authorization passing.

Open technologies

• Control system implementation continues to move

toward the use of off-the-shelf technologies such as

Microsoft Windows operating systems and standard,

open Ethernet communications

• Allow system to be more easily connected to the

enterprise or plant LAN to exchange information and

allow remote access to improve business

performance

Cyber security

• The use of open technologies exposes the control

system to the same types of security issues as the

plant LANs.

• Process control systems have traditionally been

built on proprietary technology.

• proprietary systems provide reasonable level of

security from unauthorized access due to its

closed nature

Sophistication levels in Hacking

Tools

• Past: much of problem attributed todisgruntled employees, or accidental orinadvertent actions that caused systemdisruptions.

• current threats: more from people outside

Redundancy

Concepts for

PLC/SCADA and DCS

Concept of Redundancy

addition of information, resources, or time beyond what is

needed for normal system operation.

Hardware redundancy: extra hardware for the purpose of

detecting or tolerating faults.

Software redundancy: extra software to detect, possibly

tolerate faults.

Information redundancy : extra information to implement given

function eg. ECC)

Time redundancy : For fault detection, fault tolerance;

Hardware RedundancyPassive techniques use concept of fault masking

• achieve fault tolerance without requiring action on part of

system.

• Relies on voting mechanisms.

Active techniques achieve fault tolerance

• by detecting existence of faults, performing action to remove

faulty hardware

• fault detection, fault location, fault recovery to achieve fault

tolerance.

Hybrid techniques

• combine the attractive features of passive and active

approaches.

Controller Redundant PLCs

Fault-Tolerant Unit (Fault Masking)Set of actively redundant components:

• FTUs should receive identical input messages in same order

• FTUs should operate in replica determinism

Cold standby:

• at given time only one component provides service;

• if service provider fails, failure detector starts a spare

Component

Hot standby:

• At given time, only one component provides service;

• if service provider fails, active spare component replaces

failed component

Active redundancy:

• two or more components provide the service concurrently

Triple Modular Redundancy

• Triplicate hardware, perform majority vote to

determine output of system

• If one of modules becomes faulty, remaining two

fault-free modules mask results of faulty module

at majority vote.

TMR with triplicated Voter

Troubleshooting

techniques

Instrumentation in

PLC/SCADA and DCS

Connectivity/Comm issues

• device not found

• Not Powered? Power supply overload, etc.

• Network address, bit/baud,

• Adding new device: Incorrect register address, protocol issues

• Intermittent: Noisy cable / connectors

• IO errors

Instrumentation Loop

• Open connections

• Loop impedance issues: Digital device communication issues

• Power supply noise

• Calibration / drift issues

Alarm related issues

• Unexpected alarm floods due to local

instrumentation problems

• Improper alarm settings / thresholds

Other problems

• IO card failure cause identification

• Troubleshooting and Diagnostics: Kepner-

Tregoe approach