The Internet Encyclopedia (Volume 3)

P1: JDV

Michael WL040/Bidgolio-Vol I WL040-Sample.cls June 19, 2003 16:10 Char Count= 0

68 PHYSICALSECURITY

suffer microscopic cracking ordelamination(separation

of layers). Scratches and cracks on the data (“bottom”)

side of the disc will interfere with reading data. Cracks or

delamination may also allow the incursion of air and the

subsequent deterioration of the reflective layer. That layer

is actually much closer to the label (“top”) side and there-

fore can be easily damaged by scratches or inappropriate

chemicals (from adhesives or markers) on the label side.

Although physical shocks can affect magnetic media by

partially rearranging ferromagnetic particles, a far more

common cause for magnetic realignment is, of course,

magnetic fields. The Earth’s magnetic field, averaging

about 0.5 Gauss at the surface, does no long-term, cu-

mulative damage to magnetic media. Certain electrical

devices pose hazards to magnetic media; among these are

electromagnets, motors, transformers, magnetic imaging

devices, metal detectors, and devices for activating or

deactivating inventory surveillance tags. (X-ray scanners

and inventory surveillance antennae do not pose a threat.)

Degaussers (bulk erasers) can produce fields in excess of

4,000 Gauss, strong enough to affect media not intended

for erasure. Although magnetic media are the obvious

victims of magnetic fields, some equipment can also be

damaged by strong magnetic fields.

Local Hazards

Every location presents a unique set of security chal-

lenges. There are innumerable hazards the probability

and impact of which are location-dependant. Often, a

pipeline, rail line, or road in the immediate vicinity car-

ries the most likely and most devastating potential hazard.

Two of the local hazards with the greatest impact on hu-

man life, property, and activity are flooding and geological

events.

Flooding

As many have learned too late, much flood damage oc-

curs in areas not considered flood-prone. Government

maps depicting flood potential are not necessarily use-

ful in assessing risk, because they can quickly become

outdated. One reason is construction in areas with no

recorded flood history. Another is that urbanization itself

changes drainage patterns and reduces natural absorption

of water.

Small streams react first and most rapidly to rainfall

or snowmelt. Even a very localized rain event can have a

profound effect on an unnoticed creek. Perhaps the most

dangerous situation is in arid regions, where an inter-

mittent stream may be dry or nearly dry on the surface

for much of the year. A year’s worth of rain may arrive

in an hour. Because such flash floods may come decades

apart, the threat may be unrecognized or cost-prohibitive

to address.

Usually, advance warning of floods along large rivers

is better than for the small rivers that feed them. Hav-

ing a larger watershed, large rivers react more slowly to

excessive rain or rapidly melting snow. Formation of ice

jams, breaking of ice jams, structural failure of dams, and

landslides or avalanches into lakes, however, can cause a

sudden, unexpected rise in the level of a sizeable river.

Coastal areas are occasionally subjected to two other

types of flooding. The storm surge associated with a

hurricane-like storm (in any season) can produce pro-

found and widespread damage, but advanced warning is

usually good enough to make appropriate preparations.

Moving at 725 km (450 miles) per hour on the open

ocean,tsunamis(seismic sea waves) caused by undersea

earthquakes or landslides arrive with little to no warning

and can be higher than storm surges. Although tsunamis

most often strike Pacific coastlines, a much larger (and

rarer)mega-tsunamicould effect much of the Atlantic if a

volcano in the Canary Islands collapses all at once.

An urban area is at the mercy of an artificial drainage

system, the maintenance of which is often at the mercy

of a municipality. A violent storm can itself create enough

debris to greatly diminish the system’s drainage capacity.

Not all flooding originates in bodies of water. Breaks in

water mains can occur at any time, but especially during

winter freeze-thaw cycles or excavation. Fire hydrants can

be damaged by vehicles. Pipes can leak or commodes over-

flow. Although safest from rising water, the top floor is the

first affected if the roof leaks, collapses, or is blown away.

Geological Events

Geological hazards fall into a number of categories.

These events are far more unpredictable than meteorolog-

ical events, although some, notably landslides and mud-

slides, may be triggered by weather. Earthquakes can have

widespread effects on infrastructure. The damage to an

individual structure may depend more onwhereit was

built than onhow. Buildings on fill dirt are at greater risk

because of potentialliquefaction,in which the ground be-

haves like a liquid. Earthquake predictions are currently

vague as to time and location.

Landslides and mudslides are more common after

earthquakes and rainstorms, but they can occur with no

obvious triggering event. Anticipating where slides might

occur may require professional geological consultation.

As an illustration, a cliff with layers of clay dipping to-

ward the face of the cliff is an accident waiting to happen.

Volcanic ash is one of the most abrasive substances in

nature. It can occasionally be carried great distances and

in great quantities. If it does not thoroughly clog up HVAC

air filters between outside and inside air domains, it may

still be tracked in by people. Most volcanic eruptions are

now predictable.

Humans

Humans are often referred to as the “weakest link” in

computing security, for they are the computing environ-

ment component most likely to fail. Despite their flaws,

humans have always been recognized as an essential re-

source. Before the attacks on New York and Washing-

ton, however, the sudden disappearance of large numbers

of personnel was simply not anticipated by most busi-

ness continuity planners or disaster recovery planners. All

planners, whether focused on preservation of processes

or assets, now have a different outlook on preservation

of life.

Aside from mass slaughter, there are other circum-

stances in which human resources may be lacking. Severe

weather may preclude employees from getting to work.

Labor disputes may result in strikes. These may be be-

yond the direct control of an organization if the problems