Spider-Man, TV's Lindsay Wagner, a duck puppet and a character known as Hands-Off Bill are all recent conscripts in the campaign to prevent the sexual abuse of children. Their basic message: some kinds of touching are wrong, and the child always has the right to say so.

WBZ-TV, NBC'S Boston affiliate, showed a half-hour program last week called This Secret Should Be Told, featuring Therapist-Ventriloquist Susan Linn and her two star puppets, a girl duck and a boy lion. The puppets encourage children to "tell a trusted adult" whenever they have been touched in a peculiar way.

Hands-Off Bill is the brainchild of Lloyd Martin, 42, an ex-policeman who headed the sexually-exploited-child unit of the Los Angeles police department. Using the voice of a small boy, Bill talks to children on a 30-minute audio tape constructed in the form of a radio show. The tape, along with a workbook, is sold for home use.

There are "station breaks," while the young listeners fill out workbook exercises, and scripted phone-in voices of children who talk to Bill about their experiences. Those who complete the workbook can get a certificate that says, "This special person has permission to say no to uncomfortable touching and will tell."

All of Bill's materials are based on the common finding that most would-be abusers back off quickly if a child issues a firm no. One parent told Martin that her five-year-old, a fan of Hands-Off Bill, said no to a baby-sitter who was trying to molest her. The child, added the mother, then showed the workbook to the babysitter, who read it and went for therapy.