I used to have quite a bit of spam on a forum of mine that is powered by XenForo. Real people were registering and posting crap on my forum every night. All of them were able to get through the countermeasures that were in place at the time. It stopped instantly when I found what I’m showing you today.
Thanks to this useful tip from a fellow XenForo admin, I was able to solve the problem in a simple and easy way. I just had to take a few minutes to properly set up XenForo’s stock spam management tools. No need for any additional antispam add-ons or anything.
If you’re running a XenForo powered board, make yourself a favor and check it out, it’s worth it.