Akismet , bbPress is integrated with Akismet
I wrote this up a while back. Hope it is useful.
After using numerous plugins, including Askimet, I am now using WangGuard for registration, no spammer since.
All I added with it was a security question, but this only works to prevent spam/robot registration.
for registrations i use bruteprotect it helps out alot.
bruteprotect + akismet = <3
plus combine that with bbPress’s spam control functions (throttle posting/time to edit)
bbpress uses the comment moderation settings https://codex.bbpress.org/moderation-and-blacklisting/
so combine that with the blacklist.txt from here and you should be fine
https://github.com/splorp/wordpress-comment-blacklist