RIO DE JANEIRO — The TV cooking show "MasterChef" has been a huge success in Brazil, as it has all over the world. But its Brazilian children's spin-off, "MasterChef Junior," quickly ran into problems after its first episode aired last month. There were 20 children competing, but one was quickly singled out for comments.

Twitter users began leering at a blond 12-year-old named Valentina Schulz. One man tweeted: “About this Valentina: if it’s consensual, is it pedophilia?” Another posted: “Let me keep quiet to not be jailed.”

Brazilian women were horrified — not just by the shocking content of the tweets, but also by the fact that the men posting them thought it was acceptable to do so. Tens of thousands of women took to social networks to share stories of sexual harassment and abuse they had endured as children and teenagers.

And now the country is waking up to the possibility that it may have a much bigger pedophilia problem than it realized.

Sao Paulo-based journalist Juliana de Faria, 30, is the founder of a feminist collective called Think Olga. At a TEDx event in Sao Paulo in May, she described the sexual harassment she suffered as a child. Two days after the first episode of "MasterChef Junior" was shown, she launched a campaign under the hashtag #meuprimeiroassedio — My First Harassment — in which women described similar experiences.

Within five days, Think Olga had calculated 82,000 tweets and retweets using the hashtag My First Harassment.

“The more we shared, the more people shared,” de Faria said. “We knew it was an endemic problem that happens with a lot of frequency.”

As the revelations spread on Twitter, WhatsApp and Facebook and women shared the revulsion and even blame they had felt after being harassed or abused, many of them realized something else: that close friends and relatives had suffered similar incidents but never talked about them before.

De Faria said that many women had thought their experiences were isolated, or that they were at fault.

“We don’t believe what happened. Or we blame ourselves. Or society blames us,” she said. “We are opening boxes that were always closed.”

One of those who responded to the campaign was actress Letícia Sabatella, who used Facebook to share her story of being exposed to by a man in a car when she was 12 years old, on her way home from a ballet class. She said she stared at him, picked up a brick and he drove off.

This week, Sao Paulo student Catharina Doria, 17, launched a smartphone app called Sai Pra Lá – roughly translated, “get off” or “leave me alone” – which uses GPS to register where harassment incidents took place.

A YouTube clip called "Vamos Fazer Um Scandalo," or “Let’s Make A Scandal,” also addressed the theme. In it, comedian Jout Jout Prazer (real name Julia Tolezano) noted that in a WhatsApp group of 11 friends that she is part of, every woman had a story of harassment.

“In other words, 100 percent,” she said.

The clip has been watched over a million times.

Some men have ridiculed the campaign to expose the harassment. Others have shared their own abuse stories. Male presenters of the nighttime TV talk show “Monday Chat” read out some of the women’s stories, visibly shocked.

The campaign’s success reflects the increasing activism of women in a deeply macho society, said de Faria, made possible by the Internet. Last year 45,000 people took part in a Facebook protest and posted photos of themselves with the phrase "I Don’t Deserve To Be Raped" after a survey said many Brazilians blamed victims for sexual assaults, saying they had worn revealing clothing.

“Women can go the Internet and mobilize,” she said. “They can construct their own content.”

On the cooking program, children ages 9 to 13 compete for a trophy, free groceries, a trip to Disney World and a cooking course.

Valentina’s father, Alexandre, told the news Web site IG that the family had anticipated "haters" but not perverts and was shielding Valentina from the comments.

Last week, Twitter users complained that Valentina had been reduced to a much lower-profile role on the show.

"The controversy with pedophiles happens and what does TV do? Hide Valentina in the episode. Face the problem!" tweeted one person identifying herself as Tatiana Carvalho. The network broadcasting the show, Band, denied it had made such changes. It has condemned the flood of lewd comments about the contestant, calling them "disagreeable demonstrations of extreme bad taste."