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Chapter 7 Wireless LAN
P-2612HNU-Fx User’s Guide
132
security can not only read the data passing over the airwaves, but also join the
network. Once an unauthorized person has access to the network s/he can either
steal information or introduce malware (malicious software) intended to
compromise the network. For these reasons, a variety of security systems have
been developed to ensure that only authorized people can use a wireless data
network, or understand the data carried on it.
These security standards do two things. First, they authenticate. This means that
only people presenting the right credentials (often a username and password, or a
“key” phrase) can access the network. Second, they encrypt. This means that the
information sent over the air is encoded. Only people with the code key can
understand the information, and only people who have been authenticated are
given the code key.
These security standards vary in effectiveness. Some can be broken, such as the
old Wired Equivalent Protocol (WEP). Using WEP is better than using no security at
all, but it will not keep a determined attacker out. Other security standards are
secure in themselves but can be broken if a user does not use them properly. For
example, the WPA-PSK security standard is perfectly secure if you use a long key
which is difficult for an attacker’s software to guess - for example, a twenty-letter
long string of apparently random numbers and letters - but it is not very secure if
you use a short key which is very easy to guess - for example, a three-letter word
from the dictionary.
Because of the damage that can be done by a malicious attacker, it’s not just
people who have sensitive information on their network who should use security.
Everybody who uses any wireless network should ensure that effective security is
in place.
A good way to come up with effective security keys, passwords and so on is to use
obscure information that you personally will easily remember, and to enter it in a
way that appears random and does not include real words. For example, if your
mother owns a 1970 Dodge Challenger and her favorite movie is Vanishing Point
(which you know was made in 1971) you could use “70dodchal71vanpoi” as your
security key.
Signal Problems
Because wireless networks are radio networks, their signals are subject to
limitations of distance, interference and absorption.
Problems with distance occur when the two radios are too far apart. Problems with
interference occur when other radio waves interrupt the data signal. Interference
may come from other radio transmissions, such as military or air traffic control
communications, or from machines that are coincidental emitters such as electric
motors or microwaves. Problems with absorption occur when physical objects
(such as thick walls) are between the two radios, muffling the signal.