Sunday, October 22, 2006

They know where you live

Searching a torrent indexer (for public domain content) the other day I noticed that the "find pretty girls in..." ad has got unnervingly accurate.

Forestville is the suburb right next to where I live.

How on earth do they do this? I know that there are geolocation systems that triangulate where people are by tracerouting from several locations around the globe, good for things like pre-selecting the country in a popup menu or tailoring a banner ad, but how can this work down to the suburb?

There are some services around that can figure out the ISP and your state but they're not as good as those super smart pretty girls.


Alastair said...

I used to see these ads when I was with Optus. Now on Internode they don't seem to be as closely targetted.

They could be doing this through DNS PTR lookups. IIRC Optus used to assign DNS names to their customers which were closely tied to the node (and hence suburb) of the customer.

Couple this with a traceroute to repeat the process for your nearest upstream router, and you can probably guess the location within a general part of sydney.

Still scary though. Good argument for using TOR.

whit537 said...

I've used MaxMind before, which claims 80% accuracy mapping IP address to US city. Their basic product is a data file with a C API, for which they provide a good Python binding.