kismet

802.11 layer2 wireless network detector, sniffer, and IDS

Kismet is an 802.11 layer2 wireless network detector, sniffer, and intrusion detection system. Kismet will work with any wireless card which supports raw monitoring (rfmon) mode, and can sniff 802.11a, 802.11b, and 802.11g traffic. Kismet identifies networks by passively collecting packets. In addition to standard networks, it can detect (and given time, decloak) hidden networks, and infer the presence of nonbeaconing networks via data traffic. Capture sources that are known to be supported: Atheros, Prism2, WSP100, Drone, wtapfile, pcapfile. Kismet also supports radiotap headers and should work with current FreeBSD systems.