Upside-Down-Ternet: Having Fun With Wireless Freeloaders



I'm a big fan of open wireless access points. As long as my neighbors are respectful, I've got more downstream bandwidth than I really need most of the time. That said, I can understand the frustration with having a persistant freeloader, so I can really appreciate this hack which allows you to send a "knock it off" message, without having to close down your blessed open network.

The Upside-Down-Ternet works like this:

1. You set up a DHCP server to assign addresses from one IP netblock to known MAC addresses, and another "untrusted" netblock to unknown MACs.
2. The trusted netblock is routed normally, but the untrusted netblock gets all port 80 traffic forwarded to a transparent squid proxy using iptables.
3. The squid proxy filters all HTTP traffic, looking for URLs ending in jpg or gif.
4. If a jpg or gif is encountered, the image is flipped using morgrify and the untrusted user is sent the upside down image instead of the original.

This could be easily modified to default to giving normal access. You could then direct known abusers to the crippled network. Another option would be to provide "degraded" access using a blur or desaturate filter on images. This would allow people to make use of the free service, but would require them to ask permission to be on the trusted list before having full access.
How do you like to deal with wireless interlopers? What's your ideal wireless setup - one that balances security, ease of use for legitimate visitors or passers-by, and quality of service? Give us a shout in the comments!