I think you are talking about comments containing Links to adult sites.
I had the same problem, and i was able to fix it very easyly. Just install this Plugin. The person commentating has to solve an easy math question, like “what is the sum of 1+4?”. Because Spam-Comments are often posted using Bots, and because the bots can’t solve the math-question, the spam-comments will stop.
if you need any further help, just post it here.
