Detection
A network scanner or sniffer is an application program that makes use of a wireless network interface card. It repeatedly tunes the wireless card successively to a number of radio channels. With a passive scanner this pertains only to the receiver of the wireless card, and therefore the scanning cannot be detected.
An attacker can obtain a considerable amount of information with a passive scanner, but more information may be obtained by sending crafted frames that provoke useful responses. This is called active scanning or probing. Active scanning also involves the use of the transmitter of the wireless card. The activity can therefore be detected and the wireless card can be located.
Detection is possible with an intrusion detection system for wireless networks, and locating is possible with suitable equipment.
Wireless intrusion detection systems are designed to detect anomalous behaviour. They have one or more sensors that collect SSIDs, radio channels, beacon intervals, encryption, MAC addresses, transmission speeds, and signal-to-noise ratios. Wireless intrusion detection systems maintain a registry of MAC addresses with which unknown clients are detected.
Read more about this topic: Cracking Of Wireless Networks