Build Your Own 802.11 Sniffer for $50 or So

If you have a laptop, you can build a wireless 802.11a/b/g sniffer for a cost of Atheros-based wireless card (below $50 at current market prices) and waiting time to download the 700MB ISO image. It will use Ethereal as a protocol analyzer.

The net result is pretty close to the $1,500 Airopeek. The only missing feature I know is the inability to change channels and survey them from the protocol analyzer interface.

Steps to success:

Update from Alexey Dymchenko:

# create and start normal interface
iwconfig ath0 essid dlink_test
ifconfig ath0 up
# create and start monitor interface
wlanconfig ath1 create wlandev wifi0 wlanmode monitor
ifconfig ath1 up
# enable additional RF information (not sure that Atheros driver emulates "prism2" headers well)
echo '802' > /proc/sys/net/ath1/dev_type

Other Low-Cost Wireless Sniffers

LinkFerret Network Monitor and Protocol Analyzer.

Set of monitoring utilities and packet sniffers for capture, statistical analysis, and protocol decoding. The LinkFerret network monitor is a Windows-based monitoring solution available at an affordable price.

Low-Cost Wireless Management

802.11 Network Discovery Tools

Basic open-source wireless network management tool