Massive Spam via Registration

Is there a way to secure the registration form? an image captcha? or to use the system captcha?
We get every minute a registration from a bot.

What type of registration? A new Joomla user or an event registration?
The latter shold only be possible, when you are logged in …

A new user will have a captcha code, so i really dont know how they register. but we have users with spam in username and "blogpost" domain.
 

This must be a problem with joomla user  registration. 
And then perhaps wrong  rights (to create events) in JEM genef l settings.
The event registration  of JEM needs Joomla user registration.
I think you have a joomla not a JEM problem!

ok i will check this. the normal user reg has a captcha code. but still get many emails from bot. jem will just use the core user reg? ok.

Yes, JEM uses the Joomla user registration.

For extension for spam protection see:
extensions.joomla.org/tags/spam-protection/