Hi Drosgrove,
Are you looking for protection against nasty users or looking for topic/reply protection ?
Pascal.
It depends on what you are looking for. There are plugins for all types of different captchas.
Math Captcha
Google noCAPTCHA reCAPTCHA
Honeypot (Hidden FIeld)
Questions on Registration
There are various other captchas that are there too.
https://wordpress.org/plugins/search.php?q=bbpress+captcha
If you are looking for a plugin that I think is the best out the types that I listed, pick one and I will recommend a plugin that I think is quite good to use in conjunction with bbPress.
