I can't help but wonder why you let your kids surf the net un-supervised when you've already had problems.

As with most things in life; prevention is better than cure. Most internet advisors recommend using child protection software to prevent kids from accessing inappropriate sites and or material. Try installing MADESAFE CHILD EDITION, just £2.90 from Amazon UK.

They also recommend having the computer in place where parents can monitor their childs activities on the net.

Sorry Seemysmile, but it does appear that on this occasion you'll have shut the door after the horse has bolted.