Kismet is an 802.11 layer 2 wireless network
detector, sniffer, and intrusion detection system.
It will work with any wireless card which supports
raw monitoring (rfmon) mode, and can sniff
802.11b, 802.11a, 802.11g, and 802.11n traffic
(device drivers permitting). It identifies
networks by passively collecting packets and
detecting standard named networks, detecting (and
given time, decloaking) hidden networks, and
inferring the presence of non-beaconing networks
via data traffic.