Kismet is an open source tool for discovering wireless networks. It can be used to troubleshoot a wireless network and detect network intrusions. It is a similar tool tonetstumbler (which is used in the Windows world) but it does have some differences. One area in which kismet is superior is the ability to detect hidden 802.11 wireless networks.
The significant area of difference between kismet and netstumbler is how kismet detects a 802.11 network. Kismet listens for a beacon transmission from a wireless access point; this is in contrast to netstumbler which sends broadcast for any Service Set Identifier (SSID). The advantage of listening rather than broadcasting is that kismet is able to detect networks that do not advertise an SSID.
Kismet uses channel hopping to enable detection of wireless networks. This means that it will listen on one channel, then hop to another channel and listen, then to another and so on. Channel hopping is a simple algorithm that hops from channel to channel in a pre-determined pattern. Kismet can detect a client’s response to a beacon frame and uses this to associate the client with a wireless access point.