2 cissp ® Official Study Guide Eighth Edition

Content Distribution Networks
A 
content distribution network (CDN)
, or content delivery network, is a collection of 
resource services deployed in numerous data centers across the internet in order to provide 
low latency, high performance, and high availability of the hosted content. CDNs provide 
the desired multimedia performance quality demanded by customers through the concept 
of distributed data hosts. Rather than having media content stored in a single location to 
be transmitted to all parts of the internet, the media is distributed to numerous locations 
across the internet. This results in a type of geographic and logical load-balancing. No one 
server or cluster of servers will be strained under the load of all resource requests, and the 
hosting servers are located closer to the requesting customers. The overall result is lower-
latency and higher-quality throughput. There are many CDN service providers, including 
CloudFlare, Akamai, Amazon CloudFront, CacheFly, and Level 3 Communications.
While most CDNs focus on the physical distribution of servers, client-based CDN is also 
possible. This is often referred to by the term P2P (peer-to-peer). The most widely recog-
nized P2P CDN is BitTorrent.
Wireless Networks
Wireless networking
is a popular method of connecting corporate and home systems 
because of the ease of deployment and relatively low cost. It has made networking more 
versatile than ever before. Workstations and portable systems are no longer tied to a 

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Wireless Networks 
473
cable but can roam freely within the signal range of the deployed wireless access points. 
However, with this freedom come additional vulnerabilities. Historically, wireless net-
working has been fairly insecure, mainly because of a lack of knowledge by end users 
and organizations as well as insecure default configurations set by device manufacturers. 
Wireless networks are subject to the same vulnerabilities, threats, and risks as any cabled 
network in addition to distance eavesdropping, packet sniffing, and new forms of DoS and 
intrusion. Properly managing wireless networking for reliable access as well as security 
isn’t always an easy or straightforward proposition. This section examines various wire-
less security issues.
Data emanation
is the transmission of data across electromagnetic signals. Almost all 
activities within a computer or across a network are performed using some form of data 
emanation. However, this term is often used to focus on emanations that are unwanted or 
on data that is at risk due to the emanations.
Emanations occur whenever electrons move. Movement of electrons creates a magnetic 
field. If you can read that magnetic field, you could re-create it elsewhere in order to repro-
duce the electron stream. If the original electron stream was used to communicate data, 
then the re-created electron stream is also a re-creation of the original data. This form of 
electronic eavesdropping sounds like science fiction, but it is scientific fact. The United 
States (U.S.) government has been researching emanation security since the 1950s under the 
TEMPEST project.
Protecting against eavesdropping and data theft requires a multipronged effort. First, 
you must maintain physical access control over all electronic equipment. Second, where 
physical access or proximity is still possible for unauthorized personnel, you must use 
shielded devices and media. Third, you should always transmit any sensitive data using 
secure encryption protocols.