Kismet

Kismet is a network detector, packet sniffer, and intrusion detection system for 802.11 wireless LANs. Kismet will work with any wireless card which supports raw monitoring mode, and can sniff 802.11a, 802.11b, 802.11g, and 802.11n traffic. The program runs under Linux, FreeBSD, NetBSD, OpenBSD, and Mac OS X. The client can also run on Microsoft Windows, although, aside from external drones, there's only one supported wireless hardware available as packet source.


Kismet is unlike most other wireless network detectors in that it works passively. This means that without sending any loggable packets, it is able to detect the presence of both wireless access points and wireless clients, and associate them with each other.

Kismet also includes basic wireless IDS features such as detecting active wireless sniffing programs including NetStumbler, as well as a number of wireless network attacks.
Kismet has the ability to log all sniffed packets and save them in a tcpdump/Wireshark or Airsnort compatible fileformat. Kismet also captures PPI headers.
Kismet also has the ability to detect default or "not configured" networks, probe requests, and determine what levels of wireless encryptions is used on a given access point.
To find as many networks as possible, kismet supports channelhopping. This means that it constantly changes from channel to channel non-sequentially, in a user-defined sequence with a default value that leaves big holes between channels (for example 1-6-11-2-7-12-3-8-13-4-9-14-5-10). The advantage with this method is that it will capture more packets because adjacent channels overlap.
Kismet also supports logging of the geographical coordinates of the network if the input from a GPS receiver is additionally available.