Are you doing this for an existing forum, or for a new one?
I ask because Discourse already has a lot of protections in place to make things more annoying for spammers. So if you’re starting a new site you may find that you don’t need additional verification.
For example, you can restrict permissions on new users so they can’t post links or images until they’ve used the site for a little while. You also have the option to configure Akismet for your forum, which will scan all new posts and user bios for spam, and automatically flag possible spam posts for review.
There’s also a third-party plugin that integrates with Stop Forum Spam