Your child spends a large amount of time online, especially at night. Most children who fall victim to computer-sex offenders spend enormous time online, particularly in chatrooms.
You find pornography on your child's computer. S/he may hide them in diskettes, especially when the computer is used by other family members.
Your child receives or makes calls to unknown numbers: sex offenders often engage in phone sex with children and often seek to set up an actual meeting for real sex.
Your child turns the monitor off or quickly changes the screen on the monitor when you come into the room. S/he is looking at pornographic images and doesn't want you to see them onscreen.
Your child starts withdrawing from the family. Computer sex offenders work very hard at driving a wedge between children and their families or at exploiting their relationship.