Question on forum spam

I have a tech forum that was offline for years. I then installed a brand new forum for family and friends, but I installed it in a different folder so no one would no how to get there. I then had around 400 new users in 1 hour. My site is not popular and not ranked in the search engines. I have installed 2 spam plugins and it stopped. My question is how can I make some cash from the spam people will they click adsense links etc?

Any thoughts please let me know.