Comment Re:You could troll them in return. (Score 1) 884
You don't even need to be on the Evil Twin network to do this; at least some Torrent clients have a setting for what IP address to report that you're using. Some time ago I remember researchers from one of the big-name universities (MIT?) doing this and reporting the IP address of local network printers, and successfully received DMCA notices sent to the university reporting Torrent use by the IP address of the printer.
The other thing I'll mention is that doing a "tit-for-tat" hack on the Evil Twin network is probably the wrong thing to do.
For others suggesting the use of a directional antenna -- this is trickier than it sounds. Most directional antennas (like yagis) have a narrow horizonatal beamwidth, but a very wide virtical beamwidth (when mounted for the horizonatal beamwidth -- vice-versa when mounted for the virtical beamwidth). A dish might be more pinpoint, depending on the type of feedhorn used. Likewise there's no limit to the "depth" that the signal travels -- so for instance if you think that a particular appartment building contains a transmitter you're trying to locate, it's not simple to pin down which appartment has the transmitter. This is furthermore exaserbated by reflective surfaces, including typical corrogated metal floors used in building construction. Typical direction-finding requires a set of adjustible attenuators to further localize the originating strong signnal from the weaker reflected signals. As tough as this can be in an urban environment, "DFing" (direction finding) using a directional antenna is still cheaper and more reliable than using a Doppler Scanner.