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Infrastructure Security: Devices and Media • Chapter 6 401

than data transmissions.This section focuses on the transmission of data and how to
properly secure these transmissions.

Coax

Coaxial (or coax) cable is an older type of cabling that has several different vari-
eties.These cables are used for cabling televisions, radio sets, and computer net-
works.The cable is referred to as coaxial because both the center wire and the
braided metal shield share a common axis, or centerline.There are a large number
of different types of coax cable in use today, each designed with a specific purpose
in mind.This said, many types of coax designed for a specific purpose cannot be
used for something else.
Coax cabling, which can be either thinnet or thicknet, is one of the most vulner-
able cabling methods in use. Due to its design, it is very unstable, and has no fault
tolerance.We examine why each of these coax cable types are so vulnerable.
Thin Coax

Thinnet (thin coax) looks similar to the cabling used for a television’s CATV con-
nection.Thinnet coax cabling that meets the specifications for computer networking
is of a higher quality than that used for television connections, so they are not inter-
changeable.The cable type used for thinnet is RG-58 and is specifically designed for
networking use. RG-58 has a 50-ohm resistance, whereas television cables are of
type RG-59 and have a 75-ohm resistance. Due to the way thinnet transceivers
work (as a current source rather than a voltage source), the signal going across RG-
59 cable is completely different from a signal going across an RG-58 cable.
Connections between cable segments or to computer systems are accomplished
using a T-connector on each network interface card (NIC), which allows techni-
cians to add an extra cable to the segment. In addition to having T-connectors,
both ends of a thinnet cable segment must have a terminator and one end of the
segment must be grounded.These connections are shown in Figure 6.16.
A terminator is basically a 50-ohm resistor with a Bayonet Neill Concelman
(BNC) connector. BNC connectors are the style of connectors used on the end of
thinnet cables.These connectors allow the cables to be easily connected to T-con-
nectors or barrel connectors.T-connectors are used to add a cable to an existing
segment and connect a device to the segment, whereas barrel connectors are used
to connect two coax cables together to form one cable.

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