2 cissp ® Official Study Guide Eighth Edition

Wiring Closets
Wiring closets used to be a small closet where the telecommunications cables were organized 
for the building using punch-down blocks. Today, a wiring closet is still used for organizational 
purposes, but it serves as an important infrastructure purpose as well. A modern 
wiring closet
is 
where the networking cables for a whole building or just a floor are connected to other essential 
equipment, such as patch panels, switches, routers, local area network (LAN) extenders, and 
backbone channels. Other more technical names for wiring closets include 
premises wire distri-
bution room 
and
 intermediate distribution facilities (IDF)
. It is fairly common to have one or 
more racks of interconnection devices stationed in a wiring closet (see Figure 10.1).
Larger buildings may require multiple wiring closets in order to stay within the maxi-
mum cable run limitations. For the common copper-based twisted-pair cabling, the maxi-
mum run length is 100 meters. However, in electrically noisy environments, this run length 
can be significantly reduced. Wiring closets also serve as a convenient location to link mul-
tiple floors together. In such a multistory configuration, the wiring closets are often located 
directly above or below each other on their respective floor.

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406
Chapter 10 
■
Physical Security Requirements
F I g u R e 10 .1
A typical wiring closet
Source: 
https://www.flickr.com/photos/clonedmilkmen/4390901323/
Wiring closets are also commonly used to house and manage the wiring for many other 
important elements of a building, including alarm systems, circuit breaker panels, telephone 
punch-down blocks, wireless access points, and video systems, including security cameras.
Wiring closet security is extremely important. Most of the security for a wiring closet 
focuses on preventing physical unauthorized access. If an unauthorized intruder gains 
access to the area, they may be able to steal equipment, pull or cut cables, or even plant a 
listening device. Thus, the security policy for the wiring closet should include a few ground 
rules, such as the following:
■
Never use the wiring closet as a general storage area.
■
Have adequate locks, which might include biometric elements.
■
Keep the area tidy.
■
Do not store flammable items in the area.
■
Set up video surveillance to monitor activity inside the wiring closet.

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Implement Site and Facility Security Controls 
407
■
Use a door open sensor to log entries.
■
Do not give keys to anyone except the authorized administrator.
■
Perform regular physical inspections of the wiring closet’s security and contents.
■
Include the wiring closet in the organization’s environmental management and moni-
toring, in order to ensure appropriate environmental control and monitoring, as well as 
detect damaging conditions such as flooding or fire.
It is also important to notify your building management of your wiring closet security 
policy and access restrictions. This will further reduce unauthorized access attempts.
Wiring closets are just one element of a 
cable plant management policy
. A cable plant 
is the collection of interconnected cables and intermediary devices (such as cross-connects, 
patch panels, and switches) that establish the physical network. Elements of a cable plant 
include the following:
■
Entrance facility
: Also known as the demarcation point, this is the entrance point to 
the building where the cable from the provider connects the internal cable plant.
■
Equipment room
: This is the main wiring closet for the building, often connected to or 
adjacent to the entrance facility.
■
Backbone distribution system
: This provides wired connections between the equip-
ment room and the telecommunications rooms, including cross-floor connections.
■
Telecommunications room
: Also known as the wiring closet, this serves the connec-
tion needs of a floor or a section of a large building by providing space for networking 
equipment and cabling systems. It also serves as the interconnection point between the 
backbone distribution system and the horizontal distribution system.
■
Horizontal distribution system
: This provides the connection between the telecommu-
nication room and work areas, often including cabling, cross-connection blocks, patch 
panels, and supporting hardware infrastructure (such as cable trays, cable hangers, and 
conduits).