Your child spends large amounts of time on-line, especially at night.
You find pornography or other "banned" material on your child's computer.
Your child receives telephone calls from someone (particularly an adult) you don't know, or is making telephone calls, sometimes long distance, to telephone numbers you don't recognize.
Your child receives mail, gifts, or packages from someone you don't know.
Your child turns the computer off or quickly changes the screen when you come into the room.
Your child is using an on-line account belonging to someone else.