Un fortunately there is no program smart enough to filter out most of the objectionable stuff on the internet. The best solution is no pcs in bed rooms, explain the facts of life in a sensible manner explain what perverts are and how they lure children. Block aol since it is the number one pedophiles hunting ground. Explain that you monitor all chat rooms to prevent some pervert trying to bother your child just as you make sure no one bothers them in the park.
A recent sting conducted by a tv station had over 40 perverts try to meet for sex what were they thought 13 year old girls. All of this happened on aol chat rooms for teens not some porn site. The average time from first contact until attempted meeting was less than 30 minutes. The perverts range in age from 24 to 75.