The internet seems to be full of filters trying to prevent unwanted or unauthorised entry to websites. Banks are pretty strict and demands up to four passwords and codes before you can transact anything useful on line. Other sites only want to see if you are human, and required you to punch in the letters that you are (sometimes) able to make out from a little graphics box. There are even those dubious filters that attempt to verify that you are over 18 by asking a few trivial questions from the seventies.
So, imagine that, one day, a ranting delusional massposter is finally banned by the courts of his snowy country from using the internet. You are tasked to create a filter that will protect your favourite skeptic’s forum - and arguably the unfortunate individual himself - from opening yet another account.
How would your filter look, or how would it work?