wifi scan mode

scan
The process by means of which a wireless network client finds a wireless network:

• Passive scan: walk around with a laptop looking for signals (doneaggressively, this is called warchalking, wardriving, etc.) The laptopsoftware listens for beacon frames from other wireless devices.

• Active scan: seeking a specific SSID (wireless network identifier), alaptop or other wireless device broadcasts an association request frame(also called a probe).