04.30.01
You may have noticed that the hot topic of the day has become
Wireless Local Area Network (WLAN) technology. With the costs
associated with such technology dropping in to the realm of
affordability, many network engineers see wireless as a cost-effective solution to their physical layer dilemmas. In many
instances, WLAN technology can cost less than more traditional copper-based options. This is also a technology that many home network users
are looking at due to its ease of installation. Redecorating after
tearing up walls and floors can become quite costly; with wireless
you do not have such problems.
Best Wishes,
Jay
To bring those of you up to date on how WLAN technology works, let me
give a brief overview. The version of WLAN that I am referring to is
radio wave based and defined by IEEE 802.11b. There are two pieces of
hardware that you will need to be concerned with. The first is an
access point. This piece of equipment acts as a combination of a hub
and a bridge. One side handles your wireless clients while the other
side has a common 10/100 Mbps ethernet connection for integration
into an existing LAN, or possibly to connect to a cable or DSL modem.
The other piece of hardware is the wireless network interface card,
which, as far as the end user is concerned, works pretty much the
same as a typical network interface card (NIC). More info can be
found here: www.NetworkNewz.com.
I am sure that all of you have heard that wireless technologies are
susceptible to eavesdropping because the user has little or no
control of where his/her broadcasts can be intercepted. This may be
true for some wireless technologies, such as with cordless phones;
however, security has been an issue throughout the design phase of
WLAN and its related specifications. Because of this, wireless LANs
are very secure. Let me explain why.
First of all, we need to look at how the radio waves are transmitted
(with wireless LAN) and how they differ from most other wireless
technologies. As an example, I will use cordless phones. Most
wireless devices transmit and receive on the same frequency or
"channel". What this means is that a person with a receiver set on
that frequency can intercept whatever transmission takes place. This
is how people eavesdrop on cordless telephone conversations. They
simply modify a scanner (which searches many frequencies until it
finds a "live" transmission) to receive frequencies in the range
defined for cordless devices. Cordless telephones, being analog,
usually do not scramble or encode transmissions in any way, and thus,
can be listened to on a typical scanner.
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If your wireless LAN operated in the same manner, it would not be
very secure. This is where our tax dollars have returned something to
the community. The military has developed a technique using radio
waves called "Spread Spectrum". This technique involves spreading the
transmission across several frequencies and comes in two flavors:
frequency hopping spread spectrum and direct sequence spread
spectrum. The military developed these techniques so as to avoid
eavesdropping and jamming of signals. The frequencies defined for
such use with wireless LANs are known as the ISM (industrial,
scientific, medical) bands and occupy the following ranges:
902MHZ-928MHZ and 2.4GHZ-2.484GHZ.
Frequency hopping spread spectrum basically appears to be randomly
hopping from one frequency to another. It only appears to be random -
this is part of the hardware encoding of the transmitter and the
receiver. This schedule of frequency hops would be next to impossible
to determine by simply intercepting broadcasts. You would need many
scanners checking many ranges very quickly to determine what
frequency to listen on when. Assuming that you could decipher the
order and length of stay for each hop, you would then need a device
that could listen and switch frequencies concurrently, according to
that schedule. Not easy.
Direct sequence spread spectrum is sometimes known as "pseudonoise".
This involves adding "chips" or "redundant data bits" to the data
bits. This effectively causes the transmission to be unreadable
except by a device that knows the difference between the chips and
the relevant data, in much the same way as frequency hopping spread
spectrum uses its algorithms. Again, this will require equipment and
capabilities that even the most highly skilled hacker will probably
not possess.
A hacker is more likely to determine what type of WLAN devices you
are using and obtain a like interface. He will still not be able to
connect to your network. At least he will not be able to connect in
the same manner as if he plugged a rogue machine into a wired
network. In the wired network instance, a packet sniffer or other
such device can be put to work simply by connecting to the physical
network. With wireless networks, a pre-programmed password between
the access point and the wireless interface exists. This means that a
hacker will have to negotiate a password before he even has
connectivity on the network. Difficult at best. In this respect,
wireless may be more secure than a wired network.
Lastly, most wireless LAN manufacturers include some form of
encryption. The most common type of encryption used is DES or "Data
Encryption Standard" and can include several levels of encryption. In
case you don't know, encryption encodes all transmission between the
nodes (WNIC and access point, in this example). This way, even if
information is intercepted, it is still useless; that is, unless the
hacker in question has several years to decrypt the keys used for
encryption.
In conclusion, WLAN technology is no less secure than conventional
network technology. It may not be long before most LANs are wireless.
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