glowhost is okay but it doesn't really stop all of them.. it only stops the one in their database, which all of them aren't listed in their database..
The spam protection I have on my forum makes it so I get NO kind of bot spammer what so ever. It checks to see if anyone is trying to submit the registration form (which normally takes over 45 seconds to fill out, sometimes a minute if you read all of the descriptions) too fast. A bot can fill out the form in a range from 1 second to 10 seconds naturally. I set it so if someone submits before 15 seconds, it denies the registration.. The add on can be found here, it's called Stop The Registration Bots.
https://vborg.vbsupport.ru/showthread.php?t=183917
(YES, it works fine with 3.8.x

)