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196 Chapter 4 • Communication Security: Wireless

primarily with wireless network adapters that use the Hermes chipset because of its
ability to detect multiple APs that are within range and WEP. (A list of supported
adapters is available at the NetStumbler Web site.) The most common card that uses
the Hermes chipset for use with NetStumbler is the ORiNOCO gold card.
Another advantage of the ORiNOCO card is that it supports the addition of an
external antenna, which can greatly extend the range of a wireless network.

NOTE

Wardrivers often make their own Yagi-type (tubular or cylindrical)
antennas. Instructions for doing so are easy to find on the Internet, and
effective antennas have been made out of such items as Pringles potato
chip cans. Another type of antenna that can be easily made is a dipole,
which is basically a piece of wire of a length that is a multiple of the
wavelength, cut in the center, and attached to a piece of cable that is
connected to the wireless network interface card (NIC).

One disadvantage of the Hermes chipset is it does not support promiscuous
mode, so it cannot be used to sniff network traffic. For that purpose, a wireless net-
work adapter is needed that supports the PRISM2 chipset.The majority of wireless
network adapters targeted to the consumer market use this chipset (for example,
the Linksys WPC network adapters). Sophisticated wardrivers arm themselves with
both types of cards, one for discovering wireless networks and another for cap-
turing the traffic.
In spite of the fact that NetStumbler is free, it is a sophisticated and feature-rich
product that is excellent for performing wireless site surveys. Not only can it pro-
vide detailed information on the wireless networks it detects, but it can also be
used in combination with a global positioning system (GPS) to provide exact
details on the latitude and longitude of the detected wireless networks. Figure 4.9
shows the interface of a typical NetStumbler session.

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