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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.
7.3 Before You Begin
Before you start using these screens, ask yourself the following questions. See
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if some of the terms used here do not make sense to you.
• What wireless standards do the other wireless devices support (IEEE 802.11g, for example)?
What is the most appropriate standard to use?
• What security options do the other wireless devices support (WPA-PSK, for example)? What is
the best one to use?
P-870HNU-51b User's Guide
Chapter 7 Wireless LAN
Section 7.2 on page
127
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Troubleshooting
