We've all heard of Wi-fi stealing. Some of us have suffered from it, some of us have even practised it .
But this guy, decided to do something about it. As he himself admits, the easiest thing to do would be to encrypt the signal (and please people, use WPA or WPA2 - WEP has been broken by kids a long time ago). But he found a better way to confuse the thieves - play with the content.
Using a simple Perl script, he turns every image on all HTTP connections upside down, or blurs it in a way that'd give you a headache. Of course, he makes sure it happens just to uninvited users.
I love this prank for its simplicity and the sheer fun this guy has - without causing real damage to anyone.
PS: If you'd like to know more about steal.. er, borrowing Wi Fi signals, check out this helpful article