That can be found with easier or classic methods. But let me state why you don't want others to use your internet connection. This is painfully simple and for those that disagree, let's let them live with their decision. Ready?
The short reason is that if someone used your connection for downloading a movie or something that is deemed illegal in your country then the trace leads to your connection.
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What to do with some device that doesn't do WPA2? Just one idea that works is to use what is about post 18 in this forum for a WAP that is configured for PORT 80 only use. By only allowing PORT 80 on a WAP there are no paths or ways to use file or printer shares. The devices can only find and use web servers.
Sorry if WAP, and PORTs are not in your lexicon but when you configure such things you eventually catch up.
I know that there have been published reports of somebody using clustered computers to hack WPA security, though that attack should fail if the password is sufficiently complex. Still, I suspect that people truly will be able to crack WPA at some point.
That raises a question. My home network is mixed WPA/WPA2 because some of the attached devices (eg: my Palm TX) won't do WPA2.
If/when people start successfully hacking WPA, what impact does that have on the network devices that use WPA2?
Personally I don't care too much if somebody listens in on my Palm updates - there is little of interest to hackers in the data, and I don't keep things like social security numbers in the Palm. That said, the rest of the network DOES sometimes have sensitive information. Will it still be protected when WPA is truly cracked?