Chapter 8 intentional electromagnetic interference
or IEMI, so far we have been dealing with
EMC issues where the source occurs naturally
either due to natural phenomena or due to
the inherent nature of the equipments that
we use interference created by equipments
or by lightning.
But it is also possible to intentionally create
electromagnetic fields with the sole purpose
of disturbing sensitive systems this can be
done by wrong elements in the society or even
enemy countries.
So this chapter will deal with some of the
special issues related to that type of a scenario.
The outline, so first module 8.1 we will look
at what is meant by IEMI?
What are the main characteristics and how
intentional EMI is different from the normal
electromagnetic interference issues and why
it is such a concern now?
Then after that in module 8.2 we will take
the critical infrastructure, critical infrastructure
means you know in society power lines, communication
lines, economic infrastructure so everything
that is required for the smooth functioning
of the society because often for the wrong
elements this type of critical infrastructure
is attractive target.
So we will look into what are the special
issues related with that and talk about the
mitigation philosophy applied to IEMI.
First of all what is meant by intentional
electromagnetic interference?
It is often defined by this following code
“intentional malicious generation of electromagnetic
energy introducing noise or signals into electrical
and electronic systems, thus disrupting, confusing
or damaging these systems for terrorists or
criminal purposes”.
So here there are several elements to it,
first of all in IEMI there is a component
of intension, it is something not that just
happens it is intentionally created.
So that itself introduces several challenges,
we will see that, then this whole purpose
is not any useful purpose it is for disrupting,
confusing or damaging these systems.
So it is not just accidental, then the idea
is to create chaos into that particular system
or particular establishment.
Now unintentional EMI, that is usually taken
care of legislation and standards and we have
seen EMC testing and standards in the previous
chapter and we have seen the different principles
that are used in protecting the systems.
So unintentional EMI are usually taken care
of by this type of measures and say for example
if any product is marketed in European union
the European directives requires the CE marking
that you can see in the products and other
international and national standards in EMC
are also available in all countries.
Then when it comes to aircraft you have much
more stringent condition for EMC because of
the catastrophic consequences of (EMC) EMI
into aircraft.
So there are special directives for civil
aircraft issued by civilian aviation authorities
including protection against lightning one
of the severe electromagnetic disturbance
that you can find in the aviation circles.
So all this will take care of unintentional
EMI.
Now when it comes to intentional EMI you know
it is still developing the regulations and
other things and often it is so difficult
to make regulations because often it is the
intent that creates these problems.
So in civil scenarios it is often denoted
as electromagnetic terrorism because it is
for terrorising the civil society that sometimes
you know this type of issues comes and the
levels of EMI are usually much higher the
threat levels are much higher than unintentional
EMI because there is an intention behind it.
So it is much more complicated to take care
of intentional EMI situations using the normal
civilian standards, so that is the focus of
these modules.
Now why the reasons for societies increased
vulnerability to IEMI, so why society is increasingly
vulnerable to IEMI?
So there are different reasons for that so
we can look at these reasons from let us say
from the victim side or looking from the source
side.
So from the victim side we can see that society
is extremely dependent on interconnected electrical
and electronic systems for its function, this
was not like that several decades ago.
Now imagine in advanced societies if there
is a power outage due to certain incident
you know wide spread power voltage then power
is gone communication systems will die down
soon because battery backup will be gone,
then water distribution system, transportation
system all of them are dependent upon power
and communication or financial transaction
systems.
So you can imagine a scenario in which there
is no power in the society for you know several
hours and all the systems can be disturbed
and since modern society especially in the
western societies these systems are so well
functioning that you do not often have backup,
normal homes or normal business establishment
do not have backup power generators because
power outage is such a rare phenomenon, then
increased use of sophisticated and sensitive
commercial of the shelf electronic for critical
equipments.
Now several decades ago often in critical
equipments there are especially made components
being used made for that and one can harden
the systems as one wish.
But due to the pressure to reduce cost and
other reasons often now you know commission
of the shelf equipments are used for even
for critical systems because you need so many
systems and it is often easier to buy those
things rather than mixed specifically for
those applications.
So these system are tested against normal
EMC in its normal environment, so they are
not really meant for withstanding intentionally
created EMI, when the miniaturization of components
make it that even normal level of signals
are used in the system and you do not require
that high levels of disturbance to penetrate
into a system for destroying it.
Then legal EMC requirements for civil products
are in general insufficient for protection
against IEMI because you do not expect such
high levels of source or maybe civil aircraft
is the only major exception to the rule because
there you specifies such a high level of EMI
you expect such high levels of electromagnetic
interference that civil aircraft can withstand
usually IEMI scenario.
Now on the source side you know this is kind
of a dual system when the society is becoming
more and more dependent on interconnected
electrical and communication systems for smooth
function terrorists and other criminal elements
are more attracted towards targeting those
type of systems.
So there is a motivation for them to do that
and often they can do this type of attack
anonymously because you do not leave any trace
behind unlike other type of sabotage electromagnetic
sabotage does not leave that much stress behind
because it is just a transient event.
And more components are available that can
be assembled to homemade sources, even microwave
that you use in homes as a powerful source
a powerful microwave source which couple with
antennas can be made as a good electromagnetic
weapon and there is lot of information in
the internet and expertise is widely available
nowadays and even commercial high power EM
sources can be just bought of the market like
used radars and other type of equipment are
freely available which can be converted into
weapons.
Couple with this availability of sources and
anonymity that IEMI attack often provides
becomes more attractive for the criminals
to use those type of methods.
Now a biggest concern regarding intentional
EMI is critical infrastructure for various
reasons.
You know if you have a small device with well-defined
boundary that can be measured in submitters
I mean like a cube or something you can encase
it in steel armour or you know shielding and
such protection components occurs of EMC mitigation
we have used just increase the specifications
and you can have fairly good protection against
IEMI also, but that is not possible with distributed
infrastructure.
Say for example if you take Sweden this is
map of Sweden, many of the critical infrastructure
it expands the whole country that is more
than 1000’s of kilometres and they are all
interconnected radio television network, traffic
control system, food and water supply, telecom,
power financial system, computer networks.
So if power and telecom is targeted often
the rest of these things are also will died
out, so they are all interconnected.
And the sources can be wielded by criminals,
competitors you know if it is kind of industrial
complexes, disgruntled employees there were
cases like that when disgruntled employees
were trying to sabotage their own factories
or business establishment, protestors, then
even military adversaries you know because
IEMI does not leave much trace behind and
then even without declaring a war one can
target you know other countries infrastructure
so these are the issues.
Now we have seen this classical picture from
before the basic decomposition of an EMC problem.
So you can have a source and you can have
a victim and there is a coupling path in between
source and victim.
So 2 is the coupling path, 3, 4, 5 are you
know the victim where you have this front
door kind of coupling then internal coupling
and the system plus powers etc.
Say for example a source has to be defined
for a sample frequency envelope, power, polarization,
angle of incident, etc and one of the basic
talents of EMC I mean EMI mitigation strategy
for achieving EMC is that we know something
about this source that is going to happen
in that equipments normal environment of use.
So we have some idea about frequency envelope,
power, polarization, angle of incident, source
characteristic, etc.
So this is a basic assumption, with IEMI we
do not know we cannot be sure because you
know it can be any source.
Then coupling paths of electromagnetic energy
because it is near or far field coupling,
properties of the medium whether it is conducted
coupling through cables, etc we have some
knowledge.
And receiver boundary what are the apertures,
filters or the equipment, etc.
Internal coupling of the receiver whether
things are re-radiated, what are the absorbing
materials there, ground planes this knowledge
we have.
And response of the component how the system
will respond so this is we tried to understand
all these 5 elements in a normal EMC scenario.
Even IEMI this is the same strategy that we
will be using, so there is no difference in
the approach, the only thing is that we need
to have some extra thinking to be put into
those.
So this we will see with an example later
in later in the module 2.
Now comparing IEMI to normal EMI, issues when
aiming for EMC in an IEMI scenario so let
us look into that and try to see what are
the difference between normal EMI and IEMI
situation intentional EMI situation.
First of all regarding the source in normal
EMI we assume that we know something about
the source in that particular environment
but however in the IEMI scenario it is very
hard to estimate the source characteristics
because we do not know what kind of source
the characteristics will be having.
So unconventional intentional sources are
continuously modified, so you need to have
a continuous evaluation of the perception
based on freely available technologies in
the society.
Then in normal EMI we have a fair idea of
the coupling path, say for example if you
have a building and if there is a lightning
happening to that building we know that okay
it is the air termination where the lightning
will be attaching to, but of course you can
have lightning type of pulses that can be
generated in an equipment I mean atleast small
lightning can be generated by small equipment
and if these type of things are directly injected
into a cable coming into the building or a
power socket outside then of course the building
is not designed for that type of source appearing
in that type of places.
So you can have many unconventional coupling
path because of that, so unexpected ports
for injection of disturbances, so this is
a big challenge in the IEMI scenario.
And therefore the physical and electromagnetic
topological boundaries do not coincide.
Say for example 
you know perpetrators can come into a building
with powerful sources unless there is a possibility
that these type of sources can never enter
that area.
Suppose if electromagnetic topologically we
have defined zone number 1 like that and defined
what are the sources inside zone number 1
and if we do not have a physical boundary
for that then perpetrators can bring in sources
more powerful into that particular zone.
So this is what is meant by that physical
and EM topological boundaries do not coincide
because you do not expect a lightning type
of pulse directly striking inside a building,
whereas in the IEMI scenario it is possible
to that I am just giving an example it can
be some other source necessarily lightning.
Then the philosophy of using COTS commercial
of the shelf, so that equipments are tested
for specific environments where normally it
is meant to be used and it may have very little
common with eventual IEMI environment because
the normal COTS equipment that used in a place
where you know it is not an attractive target
for perpetrators then of course it will function
in that environment but when it is used in
the environment where someone is targeting
with an IEMI source then it will not function.
So the challenge of intentional EMI we have
seen that the main difference between EMI
and IEMI is the intent and because of this
intent it is very hard to predict what resource
will be in a given situation.
So this picture you have seen what are the
possible spectra, possible EMI spectra.
Now we have to say that the whole spectra
can have the potential to be used for IEMI
attacks.
So it can be even injecting a DC current into
a ground telecommunication ground to create
disturbance.
So here in the spectra you know you have this
lightning spectra, you have normal EMI environment
spectra 10 kilohertz, 1 megahertz upto few
megahertz you can have, then you have HEMP
nuclear EMP high altitude electromagnetic
pulse that can go upto few hundred megahertz,
then you have now other type of sources used
in military and other scenarios.
For example you have narrow band high power
microwaves and high intensity radiation fields,
so they are basically short bits of sinusoidal
pulses at you know few gigahertz if you take
the frequencies so it will be very narrow
band you know like very targeted kind of band.
So military system use this, there are HPM
weapons used by military in destroying enemy
systems and all so these are narrow band system.
Then there is another type of pulse ultra
wide band so the more definition you will
see in the next page, so ultra wide band is
also a big concern.
So as the name suggest it is a impulse wave
not sinusoidal but just an impulse and impulses
have what very wide frequency bands so frequency
band can be of the order of hundreds of megahertz
for this and they are not be of extremely
high power compared to HPM maybe of less power
but then attractiveness of this as IEMI source
is that it can excite several frequency bands
in the equipment where it can introduce some
resonances and all.
So with HPM and all it is just one narrow
band and if you strengthen those narrow band
protection against those narrow bands then
of course your equipment is saved, but with
ultra wide band it exposes the system to extremely
wide frequency range and unfortunately there
can be some frequencies where the system may
go into resonances or it may be susceptible.
So this is what difference between EMI and
IEMI intent.
So the Volts frequency spectrum is open for
IEMI.
Then compromise of zoning concepts, zoning
principles may be compromised we have seen
in chapter 5 what is the electromagnetic zoning
principles like say this is zone 0, where
EMP and lightning and all kinds of things
may happen then inside you expect that this
shields and other interference, diverters
will reduce the intensity of the sources to
certain level.
So you have some idea of what these levels
should be then again to sensitive circuits
you have another zone 0, 1 and 2 so there
it will be even less.
But this is workable with naturally occurring
EMI and normal equipment EMI but if suppose
this is a big industrial complex and someone
is entering with a source hidden then immediately
you are you know breaking this electromagnetic
topology here shown boundary because there
is nothing preventing that person from entering
with a source inside.
So once can come to the most sensitive part
of the facility and you have a source that
is totally unexpected.
So compromise of zoning concepts is possible
in the IEMI scenario, topological and physical
boundaries do not coincide, you can have unusual
port of entry that normally you do not expect
and unexpected source characteristics so all
these things are possible.
Then this is especially a big challenge for
large distributed system like railways because
if it is an industrial complex or an equipment
you can have the zone boundaries like this
I mean to some extent, equipments it is possible
you can protect well I guess, even with a
physically limited industrial complex you
can try to have some sort of like a nuclear
reactor complex you can have some kind of
a control but completely distributed system
like railways, power systems, communication
system, etc it is more difficult.
Now we will see some example unexpected port
of entry, this is an example of a control
centre automatic control centre for railways
you keeping track side equipment you have
an antenna on top of this mass for communications,
etc and cables going into the building.
So nicely constructed building with shield
cladding inside, no windows, there is a perimeter
fence so access is very difficult, etc but
at the same time perimeter fence is mainly
for keeping out animals and people straying
into it you know out of curiosity not meant
for someone determined to get into the things.
Say for example you can easily scroll into
using this through these gaps, etc.
Then once you come to the building you have
equipments outside power sockets outside and
the building is on top of pillars like this
so you have all kinds of cables coming inside
so it is very easy to access the cables and
power sockets outside, but in the normal EMC
scenario you do not have to worry about it
because you do not expect any these are just
for convenience these power socket outside
for cutting the grass and other maintenance
things, but if someone is injecting in high
impulse into this then it goes into the sensitive
system inside distributed into inside or through
the cables it can be you know impulses can
be brought inside.
So this shows the unexpected port of entry
in the case of IEMI scenario.
Now there have been experiments conducted
that experiments are reported in these publications
to see the ability of differential mode ultra
wide band transients to penetrate deep into
the facility, ultra wide band have extremely
large frequencies and so often it is thought
that okay it will be dissipating very fast,
but not necessarily if it is in the differential
mode, differential mode is more like a transversal
dramatic mode with very loss very low loss.
So it can really travel a long way compared
to common mode where most of the energies
radiated out and dissipated.
So this is from a generator differential mode
signals that is injected in a building outside
the power socket between phase and neutral
or between one of these conductors on the
earth wire, then you see how it is propagating
inside after 1 meter of propagation you know
you can you have this particular level of
voltage and after 2 meters of propagation
this voltage, it is attenuating but not fast
enough, so you can penetrate deep into the
facility in the differential mode ultra wide
band.
Say what is meant by ultra wide band signal
that can be quite attractive for perpetrators
for IEMI purposes.
So these are transient signals, so this is
an example taken from this thesis that can
have rise time sub-nano seconds rise times
or even nano seconds rise times and fall times
of the order of nano seconds.
So here it is time so this is 10 nano seconds,
5 nano seconds so within few nano seconds
the pulse is over.
So this has got extremely wide band so you
can see that this is of the order of ten megahertz
here, hundred megahertz here so you can have
if you take you can have several hundreds
of megahertz in bandwidth.
So sub-nano seconds or nano seconds rise times
and nano seconds fall times unusually large
bandwidths of the order of hundred megahertz.
So due to this large bandwidth it can excite
several vulnerable frequencies within the
victim.
Now HPM are more narrow band, we have discussed
that before high power microwaves you know
shot short bush of sinusoidal waveforms separated
in time, so they are quite narrow band.
Now HPM has been you can have extremely powerful
sources with HPM, so HPM sources have everything
to do physical damage on common systems unprotected
equipments, say for example cars, personal
computers etc has been done in this publication
so this table is taken from there.
So they have seen that if you have an HPM
van so 10 megawatt source because they are
quite hug, 10 joule energy capacity.
So then you know well you do not come close
to a critical system but suppose you are 15
meter away then it can create permanent physical
damage and 50 meters it can do upset and damage
and 500 meter it can create upset and damage
so this may be one can recover from it or
one can after sometime but when the source
is ON the system is not available.
Now HPM suitcase so in a suitcase it can penetrate
much deeper into the vicinity so in the tool
close vicinity it can come to the source is
atleast thousand times less in power but still
you know hundred times less but still you
can have permanent physical damage in close
vicinity and it is a threat upto several tens
of meters.
When similar kind of effects can happen with
ultra wide band or high power microwaves 
systems but permanent damage likely requires
very high pulse repetition frequency.
So there were several tests done like this
on equipments to see what could be the possibilities
and it is known that it is possible to disturb
systems by you know sources that can be carried
in small briefcases, suitcases.
