Some ways to lock down user registration to the forum

[kn1000a 100]

Is there any captcha or "write this in the box to prove you're not a bot" tasks that we can add to the user registration page? Right now it is pretty basic and any automated systems can bypass our current registration page. 

 

If we lock this down, then there should be less spams to deal with to begin with. It's a lot to report 20+ spam messages every few weeks.