Honestly, I have always had problems with spammers leaving BS all over my wordpress sites, and the Stop Spammers plugin Version 6.12 | By Keith P. Graham, has stopped the problem completely.
The reason I ask is that Keith also says this
“I am slowing down maintenance on this plugin. I don’t have time to work on it. Don’t send me money unless you have a corporate credit card and your bosses can afford it. There is a plugin menu item to contribute. It has links for contributions and buying my books. The best way to support me is to buy me a beer at the local Blues Jam and don’t laugh when I play harmonica.”
The Stop Spammers plugin By Keith P. Graham needs to stay alive.