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Step 1: Isolate. Use a spare PC, add a NIC and use Untangle Lite (free) http://untangle.com/ which has very good. Turn off DHCP in your router, use it as an access point only. Let Untangle hand out addresses. Get the perp's MAC address and reserve his IP addresses. Use Untangle's report feature to build up a dossier of all his activities over a few weeks. See what he's doing.

Step 2: While compiling the reports, use HeatMapper (free) http://www.ekahau.com/products/heatmapper/overview.html on a notebook or netbook to locate him. It won't be any problem to find his AP in the signal map.

Step 3: After you have the data, mail him a copy of the reports and the heatmap to let him know you know what he's doing, and invite him over for a cup of coffee or other beverage of your choice. Be sure to tell him you don't want to turn him in or blackmail him, but you would like to talk geek to geek. Tell him you're going to disable WPS and change the WPA key, but you'd like him to try to hack in again, and tell you if you've left any open vulnerabilities. You can end the leeching and might just gain a buddy worth having.

Caveat: Of course you want to send a copy of the report to someone else to hand over to Law Enforcement in case he turns out to be a terrorist or freakazoid with implements of destruction to use against you.

Here's a link to the file without having to go through the whole email authentication thing, though the speed is still horrible.

http://www.ekahau.com/download/client/Ekahau%20Heatmapper-Setup.exe/

http://www.ekahau.com/products/heatmapper/overview.html is totally unavaliable

WiFi tracking with 802.11 as discussed b4 on slashdot. Bluetooth is also possible, and likely to be cheaper than active RFID as well.

The client software running on the tracked device measures the signal strength of the access points, forwards the data to the server which calculates the position. The big-brother scenario is avoided as long as you still have to install the client yourself.

The major drawback of the system is that it needs extensive calibration, since they are using not only the available access points, but also the signal strength of these. Normally they suggest calibration in a 5x5m (15x15ft) grid. More calibration points yield a more accurate result.

And now the piece of information you have all been waiting for: accuracy. With a good calibration this can yield accuracies of arround 1m. In my tests (indoor) the accuracies fluctuate a bit, but is at least better than 3m 95% of the time.

Just as the system described in the original post, Ekahau requires no extra hardware (we already have 2-300 APs on campus).

/Spiff

And it should be mentioned that the Ekahau Engine actually works quite well for indoor positioning based on 802.11 accesspoints.

A friend of mine is using it in his ph.d. project. Unfortunately, I don't have any links to the things he's done (don't think he has much online) so unfortunately I can't be more specific :-/

Since you are concerned about RF absorption, you might look at Infrared. Some supermarkets are installing ceiling mounted sensors to track shopping carts and notify shoppers of "specials" near their location.

There was also this article published a while back:

http://www.ekahau.com/pdf/NYTimes_30Oct2003.pdf

I'm currently working on my PhD project involving location based services. From my research, I've discovered that a much more accurate location estimate is possible than the simple "strongest cell tower". Basically you meassure the signal strengths from all available towers (or access points), and do some calculations based on this information. Finally you find the best match in a database of location/signal-strengths, and interpolate a position.

I first saw this technology used on WLAN. Ehahau uses this technology to provide location based services on WLAN, and it works great. In our test setup at the university, we get arround 1 meter error in the position.

I've been in touch with a group of people at The IT-University of Denmark, who are working on using this technology on GSM cellphones. The biggest problem here is getting access to the data. The cellphone companies simply do not want to provide this information. Our collaborative guess was that they want to keep this information to themselves, probably to sell extra services.

The main drawback of this technology is that a huge amount of calibration is needed to make it work. On WLAN our buildings have been calibrated in a grid of 3x3 meters, which makes quite a lot of calibration points when we want coverage of the entire campus. But the cool thing about it is that it does not require any extra hardware to do the localization. A labtop or PDA with wireless will do the job.

/Spiff

A Finnish company called Ekahau has a product called Site Survey that does map a wireless network visually and quite nicely, I might add.

We're currently planning a Wi-Fi network for our school as a final project and Site Survey seems to be a nice tool for figuring out the best places to set up APs so we get maximum coverage.

Too bad it's windows only...AND costs a bundle ( starting at $1995 afaik )

Well, you can buy lots of cool products that will thell you exactly where all your wireless clients are!

• Newbury Networks
• Ekahau
• Cirond Technologies
• PanGo Networks
• Bluesoft Inc

plus there are lots more that do other sorts of monitoring but without the geolocation angle. But I didn't just hand in a marketing assignment about them.

Make sure to also check out finnish company Ekahau for 802.11* positioning.

The same discussion seems to be popping up every 6 months or so. Check out what companies such as Ekahau and BlueSoft are offering.

Actually, location based services with WiFi are entirely possible. There are a few companies that provide just that.

For some more info check out the company's website. Here's the page on EPE. Looks like pretty neat technology. Easy to set up and accurate to within 1 meter. I doubt warchalkers will be deterred though. :)

For some more info check out the company's website. Here's the page on EPE. Looks like pretty neat technology. Easy to set up and accurate to within 1 meter. I doubt warchalkers will be deterred though. :)