I dont know how old your children are but as an 18 year old myself I have to say that if my parents started checking up on me or pointing the finger then I would start to lose respect for them. If you want to stop them looking at such content then I would suggest using a net nanny type program to block it in the first place and not bother trying to work out who it is. If you do try and monitor whats done on the computer likely the children will feel a lack of privacy (its like making them leave their bedroom door open all the time so you can see what they are doing in there). This could have an adverse effect on family realationships, also as pointed out before they may resort to looking at it in other places, I know when I was younger alot of boys on my street were to young to buy this sort of thing so they would resort to stealing it.