Are these bots and spam users caught using some sort of system in NP?
Yep, they tend to be a mixture of both bots and humans though I believe it's more common for them to be bots. Spammers are a problem through mostly all internet forums, so it isn't just one exploit in the system that's causing it.
It seems quite intriguing to me how that works and what is done to stop these bots and spammers!
There used to be an insane surge of spam-bots that flooded the forums (about one spam account made every ten minutes), so I did some looking around and found a couple plugins that are supposed to help. One is called project honeypot that does its job pretty well; after installing it, the spammers stopped nearly altogether.
I have been noticing more spammers popping up though recently, and that's most likely because I need to update the plugin; the last time I checked for updates was back in February of this year.