Some of you might receive "new private message" notification by email this days.
But once you tried to open message, you've got "Wrong message id" error.
That was spammers which I've deleted before you read your Mailbox.
 
Upgrading the wall against spammers and scammers I slightly changed registration captcha. You can look yourself, that simple verification word is very natural for us and tough for robot or some really newbie.
 
If you really like "niche related" captchas just tell that in comments and I'll show the easy way how to acheive that. For example sado-mazo site could ask something like:
The most common four letters abbreviation, first letter B (BDSM).
First name of the man who made "Windows" :) (William or Bill) etc.
 
UPD
 
To implement that open your lib.account_register.php and find:

And replace with:

or if you want different words for different languages with:

Voila!