AirSnare, a free intrusion detection system (IDS)software that able to perform similar network security functionality like physical network intrusion detection system. It works with your wireless or wired network card to monitor wireless network client activity that attached to your own wireless network.
AirSnare will alert you if any unfriendly MAC addresses or DHCP request taking place appear on your network. All new unfriendly MAC address will be turn “RED” on the AirSnare screen. Meanwhile, any traffic sent from that MAC address to the network will be logged in the Unfriendly MAC Watch Window (see to the top right) for you to determine if the MAC address really is Unfriendly or if you just perhaps missed a device on your network somewhere. Beside that, AirSnare also launching Ethereal upon a detection of unfriendly MAC address appear, which you can tracking the MAC address’s access to IP addresses and ports in details.
Beside that, You can configure AirSnare Wireless intrusion detection program to send an email notification to the administrator, log the connection, and also send a message to the connected machine, informing them that their actions are being monitored.
so, AirSnare is completely a good free intrusion detection program to detect network intruder on your wireless network.
For more on how to use AirSnare, read the AirSnare Users Guide.