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PHYSICALTHREATS TOINTEGRITY ANDAVAILABILITY OFRESOURCES 67- Asurge(sudden increase in current) due to a 1989
geomagnetic storm blew a transformer, which in turn
brought down the entire HydroQu ́ebec electric grid in 90
seconds. The periods of most intense solar activity gener-
ally coincide withSolar Max,when the cycle of sunspot
activity peaks every 10.8 years (on the average). The most
recent peak was in July 2000.
A more frequent source of surges is lightning. In ad-
dition to direct hits on power lines or a building, near-
misses can travel through the ground and enter a building
via pipes, telecommunication lines, or nails in walls. Even
cloud-to-cloud bolts can induce voltage on power lines.
Although external sources are the obvious culprits, the
reality is that most power fluctuations originate within a
facility. A common circumstance is when a device that
draws a large inductive load is turned off or on; ther-
mostatically controlled devices, such as fans and com-
pressors for cooling equipment, may turn off and on
frequently.
An ESD (electrostatic discharge) of triboelectricity
(static electricity) generated by friction can produce elec-
tromagnetic interference (see below) or aspike(momen-
tary increase in voltage) of surprisingly high voltage.
Among factors contributing to a static-prone environment
are low relative humidity (possibly a consequence of heat-
ing) and synthetic fibers in floor coverings, upholstery, and
clothing. Especially at risk is integrated circuitry that has
been removed from its antistatic packaging just before in-
stallation.
Electromagnetic Interference
Digital and analog information is transmitted over con-
ductive media by modulating an electrical current or is
broadcast by modulating an electromagnetic wave. Even
information intended to remain within one device, how-
ever, may become interference for another device. All en-
ergized wires have the potential to broadcast, and all
wires, energized or not, may receive signals. The mes-
sages may have no more meaning than the “snow” on a
television screen. Even with millions of cell phones on
the loose, much of the “electromagnetic smog” is inci-
dental, produced by devices not designed to broadcast
information.
The termsEMI(electromagnetic interference) andRFI
(radio frequency interference) are used somewhat inter-
changeably.Electrical noiseusually indicates interference
introduced via the power input, though radiated energy
may have been among the original sources of the noise;
this term is also used with regard to small spikes.EMC
(electromagnetic compatibility) is a measure of a com-
ponent’s ability neither to radiate electromagnetic energy
nor to be adversely affected by electromagnetic energy
originating externally. Good EMC makes for good neigh-
bors. The simplest example of incompatibility iscrosstalk,
when information from one cable is picked up by another
cable. By its nature, a digital signal is more likely to be
received noise-free than an analog signal.
EMI from natural sources is typically insignificant
(background radiation) or sporadic (like the pop of dis-
tant lightning heard on an amplitude modulated radio).
Occasionally, solar flares can muddle or even jam radio
communications on a planetary scale, especially at SolarMax. Fortunately, a 12-hour window for such a disruption
can be predicted days in advance.
Most EMI results from electrical devices or the wires
between. Power supply lines can also be modulated to
synchronize wall clocks within a facility; this information
can interfere with the proper functioning of computer
systems. For radiated interference, mobile phones and
other devices designed to transmit signals are a major
hazard; according to Garfinkel (2002), they have trig-
gered explosive charges in fire-extinguisher systems. Ma-
jor high-voltage power lines generate fields so powerful
that their potential impact on human health has been
called into question. Motors are infamous sources of con-
ducted noise, although they can radiate interference as
well. For an introduction to electromagnetic interference,
see the glossary and the chapter “EMI Shielding Theory”
in Chomerics (2000).Computing Infrastructure Problems
Hardware failures will still occur unexpectedly despite the
best efforts to control the computing environment. Hard-
drive crashes are one of the most infamous malfunctions,
but any electronic or mechanical device in the comput-
ing environment can fail. In this regard, critical support
equipment, such as HVAC, must not be overlooked. After
the attack on the Pentagon Building, continued computer
operations hinged on stopping the hemorrhage of chilled
water for climate control.
The Internet exists to connect computing resources.
Loss of telecommunications capabilities effectively nulli-
fies any facility whose sole purpose is to serve the out-
side world. The difficulty may originate internally or ex-
ternally. In the latter case, an organization must depend
on the problem-solving efficiency of another company. In
situations in which voice and data are carried by two sep-
arate systems, each is a possible point of failure. Although
continuity of data transfer is the highest priority, mainte-
nance of voice communications is still necessary to sup-
port the computing environment.Physical Damage
Computers can easily be victims of premeditated, impul-
sive, or accidental damage. The list of possible human acts
ranges from removing one key on a keyboard to format-
ting a hard drive to burning down a building. The focus
here is on the fundamental forces that can damage equip-
ment. Although computers and their components have
improved considerably in shock resistance, there are still
many points of potential failure due to shock. Hard drives
and laptopLCD(liquid crystal display) screens remain
particularly susceptible. More insidious are protracted,
chronic vibrations. These can occur if fixed equipment
must be located near machinery, such as HVAC equipment
or a printer. Mobile equipment that is frequently in tran-
sit is also at higher risk. Persistent vibrations can loosen
things, notably screws, that would not be dislodged by a
sharp blow.
Removable storage media are more vulnerable to dam-
age because they are more mobile and delicate. They can
be damaged by bending, even if they appear to return
to their original shape. Optical media, for instance, can