Wireless network source

You can do the usual direction-finding thing, though with reflections and multipath it can get really nasty quickly. One method that seems to work is plotting signal strength while moving around the area of the suspected peer and generating a map.

On Fri, 16 Jun 2006 08:51:17 -0400, William P.N. Smith wrote in :

It really helps to have a highly directional antenna.

snipped-for-privacy@hotmail.com hath wroth:

Yes, but it's no fun. I've done it a few times.

First you need a sniffer program that will see client radios. Netstumbler won't do that. You'll need Kismet for Linux. This is best run from one of the LiveCD distributions. No need to reformat your laptop hard disk.

Next, you'll need a supported wireless card with an external antenna connector. There are some PCMCIA cards that have connectors, but methinks the USB radios with the flip up antennas are probably a good substitute. The radio will need to be shielded, the antenna removed, and a connector attached. Next, you'll need a directional antenna. This part is critical as any side lobes are guaranteed to cause difficulties in determining the direction. A commerical dish antenna is usually best. 24dBi is too big to handle easily. I use the 19dBi size. I found the typical barbeque grill antenna leaks a bit out the back, so I just covered the dish with aluminum foil. An 18" DBS pizza dish does NOT work well.

You'll need some practice using this affair. The correct way is to use a map. Orient the map in the proper compass direction and draw a line through your known location to the direction where the signal is coming from. Then, move approximately perpendicular to this line and draw another line. Do as many lines as practical. Many of these will miss horribly because of reflections. Where the majority of the lines intersect is the culprit.

Direction finding tends to break down when you get close to the signal source. You may need a coaxial attenuator between the antenna and the receiver to prevent overload. This also where receiver shielding becomes important.

Good luck.