Parental controls in Linux

[WipeOut]

Hi,

Is there anything for parental control that works on Linux??

I have a friend who has a son that enjoys the internet, he had windows 
on his PC but in less than a week completely destroyed the install 
because of all the stuff he installed..

So we moved him onto a Linux system and so far its working great..

The problem now is that he is getting far to wrapped up in looking at 
porn and not the innocent kind..

Is there any parental control software for Linux available??


Thanks..