Forum spam is annoying for forum administrators and members alike. Put a stop to it on your bbPress forums with the new bbPress reCaptcha plugin. It adds reCaptcha protection to your topic reply forums.
Install and activate the plugin and then turn it on by going to the settings and entering your Public and Private keys. It will make a dramatic difference in the amount of spam you receive on your forum, and may even eliminate it altogether. If any spam bots are able to get past your registration form, at least they won’t be able to junk up your forums with spammy replies. Check out a demo at the plugin developer’s example site. Download bbPress reCaptcha from the WordPress plugin repository.