Lastly, Aironet wireless LAN cards will require some modification to access the external antenna connector. This modification involves removing the top cover of the antenna section of the card (Spurrier, p.1).
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Finally, investigate how the antenna is mounted. Since you will be attaching the antenna to your car, magnetic-mount antennas are preferable.
Under FCC law, if you are using an omni-directional antenna in the 2.4 Ghz range, your rig must not exceed a total output of 1 watt, or 30 dBi (Federal Communications Commission, p.90) (Pozar, p.3) (Young, p.3). Since many wireless LAN cards produce an output that is well under this limit, an external antenna is used to increase the overall power output.
There are two main antenna behaviors: directional and omni-directional. Directional antennas are primarily used for fixed point-to-point wireless transmissions. These antennas are unpopular amongst wardrivers because they focus the radio wave transmission and reception in one specific direction. Since the task of a wardriver is to scan an entire area for access points, the only logical antenna choice is an omni- directional antenna. Many omni-directional antennas take the form of whips or blades that offer between 4 and 15.4 dBi power increases (Schafer, p.1).
External antennas are not a requirement to participate in the wardriving activity, however, any equipment that can be used to extend the range of a wireless LAN card will allow one to detect more wireless access points with less distance traveled. Antennas come is a variety of sizes, shapes and specifications and they have become the defining aspect of a wardriving rig. Since 802.11b wireless networks operate in the 2.4 Gehz ispectrunm,=a proper wardriving8antenna will support this same frequency.
Attaching an external antenna to a wireless LAN card will require the use of a cable called a pigtail (Positive, p.1). A pigtail is usually a short 1 to 2 foot cable that converts connectors from your wireless LAN card’s proprietary connector to a standard antenna connector. An N-male connector is usually used for the other end of the pigtail and it connects with the N-female cable of the antenna.
Most wireless cards, combined with a 15.4 dBi omni-directional antenna, will achieve power levels very close to the 1-watt FCC limit. However, many wardrivers become fanatical about increasing the range of their wireless cards and may opt to employ the use ofyannamplifier. ASome wardrivers9may use a 500mWBor01 watt1a6mplifie6r to overcome signal loss produced by long cables and multiple cable connectors. While there is no documentation of wardriving rigs that include amplifiers above 1 watt, amplifiers can be found in varieties of up to 50 watts.
© SANS Institute 2002,
As part of the Information Security Reading Room.
Author retains full rights.