If you are already using WPA2 with MAC address filtering and they still get in then you could consider the following ideas.
Use a REALLY long random password which will take forever to crack and change it frequently.
OR
Although I could never legally reccomend this (lets call this a theory), a way to more than likely permanently "scare them off" would be to capture all of their traffic and note all of their credentials. Then confront them with "non-public information about themselves" off of one of their social media sites, etc. If that's not enough, they could "re-unite with their Ex publically which could stir some things up with the current partner" however this might open you up to legal action against you so again I can not advise it, I would only call it a "theoritical application".
OR
Email them (get their email address(es) by sniffing their traffic) that you are monitoring your network and that you have all LOGS that they are connecting without permission and that you will be suing them for the use of your bandwidth and report them directly to any organizations if they are breaking any laws (illegally downloading movies, music, etc. since your Internet provider will hold YOU responsible for what's done on your network). I would look up small claims court in your state and see what the maximum damages are allowed and file suit. Also if you can get video with audio or even just audio recordings of the neighbor telling you off while admitting guilt that they are digitally tresspassing and stealing you may be able to use that in court depending on your state without getting permission from them to record everything. If you can use the recordings, I don't know a judge who wouldn't rule in your favor regardless of how computarded they might be since the neighbor admitted guilt in a recording.
Good luck.
17If you're really concerned I'd whitelist MAC addresses too. Yes, they can be spoofed, but it's an extra layer of hassle that someone has to go through and might be enough to put them off. – ChrisF – 2012-03-28T12:37:50.763
Already done that ,its just that i hate freeloaders and dont really like that they would be helping themselves to other peoples bandwidth – Shekhar – 2012-03-28T12:48:50.057
1The only way to break WPA2+AES is by trying every combination possible. This is of course only true if you disable WPS. – Ramhound – 2012-03-28T14:13:33.743
8
A counterpoint to all the people complaining about "freeloaders": Why We Need An Open Wireless Movement
– endolith – 2012-03-28T15:10:20.673@endolith I'm all for open WiFi, but while individuals are paying for their own, theft is not the answer. – Aaron Bertrand – 2012-03-28T15:34:15.260
Can't you go round to their house? – Chris S – 2012-03-28T15:40:36.953
@AaronBertrand: It's not theft, and the people paying for their access aren't being harmed by others using it. – endolith – 2012-03-28T15:45:55.163
3@endolith really? What about people with data caps, or who pay by the MB, or are trying to download large ISOs and their bandwidth is crowded by people watching porn on borrowed WiFi instead of paying for their own? – Aaron Bertrand – 2012-03-28T15:56:56.603
4It might not literally be theft, but that's essentially what it is if you break into my WEP network to gain access to the line I paid for. You are taking away some of my speed, some of my bandwidth and you are potentially exposing me to criminal charges if you misuse the network. Saying it is not theft is completely ridiculous. – gparent – 2012-03-28T15:57:51.710
1Using someone else's wifi is most certainly not theft, but some might consider it trespassing. – Eroen – 2012-03-28T16:08:49.840
@gparent in most jurisdictions, you are not potentially exposed to criminal charges because someone is able to use your WiFi. Also, I think in a lot of jurisdictions accessing bad protected WiFi's is not even a crime, but that is a different question. Edit: do note that if you are actively altering/filtering the traffic, the legal situation may change as you are now actively taking part into their usage of the network! – Legolas – 2012-03-28T16:36:25.163
1@Legolas I should've made my point more clear: the simple risk of being accused and having to defend yourself in court is, to me, a good enough reason not to have an open network, whether you would be charged guilty or not. – gparent – 2012-03-28T16:50:44.077
@gparent: WEP-protected ≠ "open wireless" – endolith – 2012-03-28T18:37:26.743
@Eroen: You mean the person running the Wi-Fi node is trespassing by broadcasting their signal onto my property, right? :) – endolith – 2012-03-28T18:42:24.257
@endolith: Obviously. Did you know that 0 does not equal 1? – gparent – 2012-03-28T18:44:30.343
@endolith: Nah, we've go the ITU to bestow Glorious Freedoms upon us for EIRP <= -10 dBW, f in [2.4, 2.4835] GHz (provided int_f^{f+1 MHz} EIRP(v) dv <= -20 dBW for all f)
– Eroen – 2012-03-28T19:05:18.960