Implementing a solution where bad strings are not allowed is always fun. Had to create a gig long list of warranty registration codes a while back where it wasn't just the swear words that were naughty. There were also a few product specific words as you can't have 'FAIL' or 'SNAP' as part of a warranty registration code.

Other words that had to go included 'Jew'. Nothing 'naughty' about the word it just didn't look good in the codes so that had to be added to the big, long list of mostly 'naughty' words.

We also used a reduced dictionary so that codes could be given out over the phone without people getting it wrong, so no '1, l, L' problem or '0, o, O' problem.

I didn't find a handy library for our exact requirements and, as a consequence, I would advise people to roll their own code for such applications.

The fun part was making my non-technical manager in charge of the big, long list of rude words. I think that his additions were the only contribution to 'code' that he ever made.