ZyXEL P-663HN-51 Manuel d'utilisateur télécharger pdf (Page 143)

Chapter 18 Wireless LAN

P-663HN-51 User’s Guide

143

Radio Channels

In the radio spectrum, there are certain frequency bands allocated for unlicensed,

civilian use. For the purposes of wireless networking, these bands are divided into

numerous channels. This allows a variety of networks to exist in the same place

without interfering with one another. When you create a network, you must select

a channel to use.

Since the available unlicensed spectrum varies from one country to another, the

number of available channels also varies.

Wireless Security

By their nature, radio communications are simple to intercept. For wireless data

networks, this means that anyone within range of a wireless network without

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

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ZyXEL P-663HN-51 Manuel d'utilisateur Page 143