Ad ances in Elec ical and Elec onic Enginee ing
136
IT SECURITY ASPECTS OF INDUSTRIAL CONTROL SYSTEMS
P. Holeko, I. K bilo á
Uni e si y o Zilina, Facul y o Elec ical Enginee ing, Depa men o In o ma ion and Con ol Sys ems
Uni e zi na 1, SK 010 26, Zilina, Slo ak epublic
E-mail: pe e .holecko@ el.u c.sk, izabela.k bi[email p o ec ed].sk
Summa y This pape discusses a se o gene al ne wo k sys em a chi ec u es o indus ial p ocess con ol sys ems as well as
ulne abili ies ela ed o hese sys ems and he IT h ea s hese sys ems a e exposed o om he poin o iew o Common
C i e ia me hodology and ITU-T ecommenda ion X.805.
1. INTRODUCTION
Real- ime con ol sys ems used in p ocess
con ol applica ions ha e many cha ac e is ics
di e en han adi ional p ocess in o ma ion
sys ems. Fo emos among hese is design o
e iciency and ime-c i ical esponse. Secu i y is
gene ally no a s ong design mo i a ion and
he e o e ends o ge ou o way o pe o mance.
Compu ing esou ces a ailable o pe o m o
secu i y unc ions a e o en e y limi ed.
2. PROCESS CONTROL SYSTEMS
Digi al indus ial con ol sys ems can be
classi ied in o p ocess-based sys ems o disc e e-
based sys ems. P ocess-based con ols a e used o
con ol a con inuous p ocess such as uel low in a
powe plan o pe oleum in a e ine y. Disc e e-
based con ols (also known as ba ch con ols)
con ol disc e e pa s manu ac u ing o “ba ches” o
ma e ial like in a chemical plan . Bo h ypes o
con ol u ilize he same ypes o con ol sys ems,
senso s, and ne wo ks.
Figu e 1 shows he key con ol componen s o
an indus ial con ol sys em, including he con ol
loop, he human – machine in e ace (HMI), and
emo e diagnos ics and main enance u ili ies [1]. A
con ol loop consis s o senso s, con ol ha dwa e,
p ocess ac ua o s, and communica ion o
measu emen a iables. Measu emen a iables a e
ansmi ed o he con olle om he p ocess
senso s. The con olle in e p e s he signals and
gene a es he co esponding con ol signals ha i
ansmi s o he p ocess ac ua o s. P ocess changes
esul in change o senso signals, iden i ying he
s a e o he p ocess.
The human – machine in e ace allows a con ol
enginee o ope a o o con igu e se poin s, con ol
algo i hms and pa ame e s in he con olle . The
HMI also p o ides displays o p ocess s a us
in o ma ion, ala ms, and o he ele an da a.
Diagnos ic and main enance ools, o en a ailable
ia modem and In e ne in e aces, allow con ol
enginee s, ope a o s and endo s o moni o and
modi y con olle , senso , and ac ua o p ope ies
om emo e loca ions.
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Fig.1 Main con ol componen s
A ypical indus ial con ol sys em con ains an
ex ension o con ol loops, HMIs and Remo e
Diagnos ics and Main enance ools buil on an a ay
o ne wo k p o ocols. Supe iso y le el loops and
lowe le el loops ope a e con inuously o e he
du a ion o a p ocess a cycle imes anging on he
o de o minu es o milliseconds.
In a la ge en e p ise, he e may be se e al
geog aphically dis ibu ed indus ial plan s.
En e p ise business ope a ions can access plan
in o ma ion o e he In e ne o in some cases o e a
wide a ea ne wo k (WAN).
The local a ea ne wo k (LAN) o a p ocessing
plan se ices all o he ope a ions wi hin he plan
while he ac ual con ol sys em o he plan si s on a
somewha isola ed pee - o-pee ne wo k. A his
le el he sys ems can be ca ego ized in o wo ypes
o supe iso y based con ol schemes, Dis ibu ed
Con ol Sys ems (DCS) and Supe iso y and Da a
Acquisi ion Sys ems (SCADA). DCS a e used o
con ol la ge complex p ocesses such as powe
plan s, e ine ies o chemical plan s ypically a a
single delimi ed si e. By con as , SCADA a e used
o con ol mo e dispe sed asse s whe e cen alized
da a acquisi ion is as impo an as con ol. Examples
o SCADA applica ions a e he wa e , gas, and
elec ical ene gy dis ibu ion ope a ions.
The gene al ne wo k a chi ec u es o DCS and
SCADA a e shown in Figu e 2. By compa ison o
hese schemes we can see ha a a highe le el o
ne wo k a chi ec u e, he pe o med plan ope a ions
a e simila o plan s using ei he DCS o SCADA
sys ems. A his le el, e e y hing esides on a local
IT secu i y aspec s o indus ial con ol sys ems
137
a ea ne wo k. Componen s include gene al pu pose
wo ks a ions, p in e s, da abases, applica ion se e s
and domain con olle s. Communica ion ou side he
plan is ypically es ablished ia In e ne o WAN
using a i ewall. The DCS and local SCADA
componen s o a plan ypically ope a e on a pee - o-
pee ne wo k.
A DCS is comp ised o a supe iso y laye o
con ol and one o se e al dis ibu ed con olle uni s
wi hin he same p ocessing plan . The supe iso y
con olle uns on he con ol se e and
communica es wi h i s subo dina e uni s ia a pee -
o-pee ne wo k. The supe iso sends se poin s and
ecei es da a om dis ibu ed con olle s. The
dis ibu ed con olle s con ol hei associa ed
p ocess ac ua o s based on eques s om he
supe iso and p ocess senso s eedback. The
communica ion o con olle wi h i s senso s and
ac ua o s is ypically ealized using a local ield bus
elimina ing he need o poin - o-poin connec ion
be ween he con olle and each o hese de ices.
The e a e se e al ypes o con ol uni s used in
dis ibu ed con ol poin s o a DCS. In dependence
o applica ion he mos widesp ead a e machine
con olle s, p og ammable logic con olle s (PLC),
p ocess con olle s and single loop con olle s.
A ypical SCADA consis s o a Cen al
Moni o ing Sys em (CMS) and one o mo e Remo e
S a ions (RST). The CMS houses he Con ol Se e
and he communica ion ou e s ia a pee - o-pee
ne wo k, collec s and logs in o ma ion ga he ed
om by he emo e s a ions and gene a es necessa y
ac ions. A emo e s a ion consis s o ei he a Remo e
Te minal Uni (RTU) o a PLC which con ols
ac ua o s and moni o s senso s. In mos cases he
RST has a capabili y o diagnos ic and epai
unc ions in e aced ia some ype o po able
compu e . The communica ion channel be ween
emo e s a ions and he CMS is ealized using
me allic line, op ical line o adio equency wi h
epea e s, whe e necessa y.
Ne wo ked con ol sys em a chi ec u es which
include con inuous ope a ions o ans o ma ion o
aw ma e ials in o usable p oduc s, ollow he DCS
scena io. On he o he hand, he ne wo k
a chi ec u es suppo ing dis ibu ion ope a ions o
usable p oduc s, copy he s uc u e o SCADA.
3. VULNERABILITIES AND IT THREATS
As we said be o e, in he sphe e o p ocess
con ol, he IT secu i y has been o minimum
impo ance. Sys ems we e p ima ily designed o
mee pe o mance, eliabili y, sa e y, and lexibili y
equi emen s and we e ypically physically isola ed
and based on p op ie a y ha dwa e and
communica ion sys ems. The in oduc ion o
In e ne based in o ma ion echnology wi hin he
p ocess con ols indus y has inc eased
ulne abili ies o he indus y’s compu e sys ems.
Cen alized ope a ion and emo e main enance o
indus y sys ems pe o med o e public
elecommunica ion ne wo ks p o ides po en iali ies
o h ea ening in luences o his c i ical
in as uc u e. DCS and SCADA sys ems ha
ope a e on comme cial ha dwa e and so wa e,
combined wi h connec ions o ex e nal ne wo ks,
allow a simpli ied in asion and possible de as a ion
o hese sys ems. In he su ey [2] which has been
pe o med on a sample o o ganiza ions wi h 100
and mo e employees in di e en sec ions o
indus y, business, se ices, and s a e adminis a ion,
75% o esponden s poin ed he occu ence o
secu i y inciden s caused by i uses, 28% caused by
LAN ailu e, and 24% due o WAN ailu e. The
ea s can o igina e in di e en sou ces: despi e ul
in ade , e o is g oup, disg un led employe ,
hos ile go e nmen , bu also acciden and na u al
disas e .
Fig.2 Example o DCS and SCADA a chi ec u es
LAN
Wo ks a ion
HMI
Hub/swi ch
pee - o-pee ne wo k
PLC
senso s/
ac ua o s
senso s/
ac ua o s
senso s/
ac ua o s
senso s/
ac ua o s
HMI
Machine
Con olle
P ocess
Con olle
Single
Loop
Con olle
LAN
Wo ks a ion
HMI
Hub/swi ch
In e ne /WAN
Con ol se e
Dis ibu ed plan
pee - o-pee ne wo k
RTU/PLC RTU/PLC
senso s/
ac ua o s
senso s/
ac ua o s
RST RST
RTU/PLC RTU/PLC
senso s/
ac ua o s
senso s/
ac ua o s
RST RST
Con ol se e
SCADA DCS
Ad ances in Elec ical and Elec onic Enginee ing
138
4. THE COMMON CRITERIA (CC)
PROJECT
The goal o he Common C i e ia (CC) p ojec
was o de elop a s anda dized me hodology o
speci ying, designing, and e alua ing IT p oduc s
ha pe o m secu i y unc ions which would be
widely ecognized and yield consis en , epea able
esul s independen ly o echnology and
implemen a ion [3].
The h ee-pa CC s anda d ISO/IEC 15408, and
he CEM a e wo majo componen s o he CC
me hodology, as shown in Fig. 3.
Fig.3 Majo componen s o he CC/CEM
Fou key concep s a e p esen ed in Pa 1 o he
s anda d:
1. P o ec ion P o iles (PPs),
2. Secu i y Ta ge s (STs),
3. Ta ge s o E alua ion (TOEs),
4. Packages.
A P o ec ion P o ile is an implemen a ion-
independen se o secu i y equi emen s o a
ca ego y o TOEs ha mee speci ic consume needs
[4]. Secu i y Ta ge deno es a se o secu i y
equi emen s and speci ica ions o be used as he
basis o e alua ion o an iden i ied TOE. Ta ge o
E alua ion is an IT p oduc o sys em and i s
associa ed adminis a o and use guidance
documen a ion ha is he subjec o an e alua ion. A
package is a eusable se o ei he unc ional o
assu ance componen s (e.g. an E alua ion Assu ance
Le els), combined oge he o sa is y a se o
iden i ied secu i y objec i es.
5. ITU-T RECOMMENDATION X.805
The Recommenda ion de ines gene al secu i y-
ela ed a chi ec u al elemen s ha app op ia ely
applied can p o ide end- o-end ne wo k secu i y [5].
The a chi ec u e shown in Fig. 4 can be used
wi h di e en ne wo k elemen s, se ices, and
applica ions in o de o de ec , p edic , and co ec
secu i y ulne abili ies.
Fig. 4 Secu i y a chi ec u e o ne wo k secu i y
A Secu i y Dimension is a se o secu i y
measu es designed o add ess a pa icula aspec o
he ne wo k secu i y. The Recommenda ion X.805
iden i ies eigh such se s ha p o ec agains all
majo secu i y h ea s: 1. Access Con ol, 2.
Au hen ica ion, 3. Non- epudia ion, 4. Da a
Con iden iali y, 5. Communica ion Secu i y, 6. Da a
In eg i y, 7. A ailabili y, and 8. P i acy.
In o de o o e he lexibili y o coun e ing he
po en ial h ea s he e a e h ee secu i y laye s
de ined: he In as uc u e Laye , he Se ice Laye ,
and he Applica ion Laye . The secu i y Laye s
iden i y whe e secu i y mus be add essed in
elemen s and sys ems by p o iding a sequen ial
pe spec i e o ne wo k secu i y.
The Managemen Secu i y Plane, he Con ol
Secu i y Plane, and he End-Use Plane a e a ce ain
ype o ne wo k ac i i y p o ec ed by Secu i y
Dimensions. Ne wo ks should be designed in such a
way ha e en s occu ed on one Secu i y Plane a e
kep o ally isola ed om he o he Secu i y Planes.
The a chi ec u e iden i ies secu i y issues ha
need o be add essed in o de o p e en bo h
in en ional as well as acciden al h ea s. The
ollowing h ea s a e desc ibed [6]:
 des uc ion o in o ma ion and/o o he
esou ces,
 co up ion o modi ica ion o in o ma ion,
 he , emo al o loss o in o ma ion and/o
o he esou ces,
 disclosu e o in o ma ion,
 in e up ion o se ices.
The in e sec ion o each Secu i y Laye wi h
each Secu i y Plane ep esen s a secu i y pe spec i e
IT secu i y aspec s o indus ial con ol sys ems
139
whe e Secu i y Dimensions a e applied o coun e ac
he h ea s. Table 1 shows mapping o Secu i y
Dimensions o he designa ed secu i y h ea s.
Table 1 Mapping Secu i y Dimensions o secu i y
h ea s
6. CONCLUSION
P e iously we in oduced he issue o secu ing
dis ibu ed indus ial p ocess con ol sys ems build
on DCS o SCADA sys em a chi ec u e wi h WAN
o In e ne connec i i y. Such connec i i y o public
accessible ne wo ks makes hese sys ems po en ial
a ge s o a acks on hei ulne abili ies.
The objec i e o ITU-T Recommenda ion X.805
is o gi e de elope s a comp ehensi e op-down
basis o c ea ion o de ailed ecommenda ions o
he end- o-end ne wo k secu i y independen ly o he
ne wo k’s unde lying in o ma ion echnology o
p o ocol s ack.
The Common C i e ia p ojec is applicable as a
guide o he e alua ion o sys ems wi h IT secu i y
unc ions and IT secu i y measu es implemen ed in
ha dwa e, i mwa e, o so wa e. The speci ic Ta ge
o E alua ion can be a pa icula ne wo k elemen
bu also an en i e subsys em o ne wo k.
Usage o combina ion o hese amewo ks in
design, implemen a ion and e alua ion o dis ibu ed
con ol sys ems applied in oday’s indus y will lead
o minimiza ion o secu i y h ea s impac s.
Fu he wo k in ield o applica ion and
de elopmen o me hodologies o inc easing
secu i y o dis ibu ed indus ial con ol sys ems will
con inue.
REFERENCES
[1] Falco, J., S ou e , K., Wa e ing, A., P oc o ,
F.: IT Secu i y o Indus ial Con ol Sys ems.
Na ional Ins i u e o S anda ds and Technology,
Gai he sbu g (2002).
[2] In o ma ion Secu i y Su ey in he Slo ak
Republic 2004. KPGM Slo ensko, DSM – da a
secu i y managemen , NSA SR (2005).
[3] He mann, D.S.: Using he Common C i e ia
o IT Secu i y E alua ion. Aue bach
Publica ions (2003).
[4] Common C i e ia o In o ma ion Sys em
Secu i y E alua ion, Ve sion 2.1, (1999).
[5] D a ITU-T Recommenda ion X.805 (Fo me ly
X.css), Secu i y a chi ec u e o sys ems
p o iding end- o-end communica ions. ITU
(2003).
[6] CCITT Recommenda ion X.800, Secu i y
a chi ec u e o Open Sys ems In e connec ion
o CCITT applica ions. CCITT, Gene a
(1999).
SECURITY
THREAT
SECURITY
DIMENSION
Des uc ion
Co up ion,
Modi ica ion
The ,
Remo al, Loss
Disclosu e
In e up ion
Access Con ol
 


Au hen ica ion


Non-
Repudia ion





Da a
Con iden iali y


Comm. Secu i y


Da a In eg i y


A ailabili y


P i acy
