Thanks all for the feedback!

The impression I get from reading your posts is that while YaBB is a feature-rich, easy-to-use, free board, it's lacking in security features. Aristotle also pointed out that it has lots of textfiles. Yah, that's something I don't like about it too. Also, I'm sure some of the perl files can be combined to make it easier to have overall view of what the code is doing. It thus seems that suitable hacking of the code may be necessary to improve on the security aspect if one is thinking of using it.

Regarding NMN's webboard, I've that too. But while I've no doubt that the coding is of high quality, I do think it's lacking in lots of other features - the look and feel, user-friendliness, etc.