The easiest way to punish them, or teach them a lesson, is like this:
- Assign a static IP to their device.
- Move out to your Internet’s dmz
3. Watch how quickly they will lament to the influx of viruses, etc that it becomes exposed to.
4. Setup a static routing of internet traffic to/from their system to some inappropriate website.Now if that isn’t enough, just block their device’s mac address. Then change your device wireless password, set a login password for the router and perform a cold boot. That will physically cut their internet connection, and keep them from reconnecting.
But this really begs the questions, how did they they get on your wireless connection in the first place, how did they remain for so long, why didn’t you cut them off a long time ago, and why didn’t you perform some simple basic security setups to prevent this in the first place?