[jewel]

In order to make a map of which wireless LANs are available, you switch the radio in receive mode and then cycle through the channels, capturing all packets. Then, you filter the packets for beacons. I believe when you "scan" for wireless networks, your wireless device is going to be doing something similar under the hood.

It'd be easy to accidentally leave debug logging turned on for the parsing code. Alternatively, if you use something off-the-shelf like kismet, the packet logs are saved in /var/log/kismet automatically.