Hiba Bég, a graduate student in the United States, was visiting the grave of her grandmother in New Delhi over the weekend when she learned that she was “for sale” to the highest bidder online — for a second time in less than a year.

Her screen filled with dozens of calls and messages from friends, all sharing the same screenshot of the profile created of her on the app, a fake auction site called “Bulli Bai.” Ms. Bég, a former journalist with an active online presence, wasn’t alone. More than 100 other prominent Indian Muslim women, including artists, journalists, activists and lawyers, found that online images of themselves were being used without permission on the app, which went up on Saturday and was taken down again within about 24 hours.

In June a similar app, called “Sulli Deals,” appeared. (Both terms are derogatory slang for Muslim women.) That one remained up for weeks and was taken down only after complaints from victims. Though the police opened an investigation, no one has been charged in that case.

India’s online space is rife with misogyny and harassment of women. But the two “auctions” have amplified concern about the organized nature of the virtual bullying, and how targeted smears and threats of violence, particularly sexual violence, are deployed to try to silence women, especially those critical of some of Prime Minister Narendra Modi’s policies.

“The intimidation is aimed at forcing Muslim women who raise their voices against the injustice to withdraw from public life,” said Ms. Bég, 26, who is pursuing a graduate degree at Columbia University. “But you don’t back off, even if everything gets overwhelming.”

Muslim women were at the forefront of one of India’s largest protest movements in recent decades. In early 2020, before the coronavirus pandemic began in earnest in India, thousands blocked roads and held demonstrations in protest of a new citizenship law that was seen as prejudiced against Muslims.

Women featured in the “auction” included Fatima Nafees, the mother of a student activist who disappeared more than five years ago after a fight with members of a right-wing student organization; a film star turned social activist, a researcher, and several other prominent Muslim women.

Both the app that went up in June and the more recent one were hosted by GitHub, a Microsoft-owned open software development site based in San Francisco. On Sunday, India’s federal minister for communications, Ashwini Vaishnaw, said that GitHub had blocked the user behind the recent app. GitHub has not commented publicly on the episode.

Karti Chidambaram, a member of India’s Parliament and a leader of the opposition Congress party, wrote on Twitter that he was appalled that those responsible apparently felt emboldened because of the government’s lack of action on the previous auction.

“It is unacceptable that this project of dangerous anti-Muslim misogyny is back,” he said.

On Monday, the police in the southern state of Andhra Pradesh said they had opened an investigation and filed a criminal complaint against several Twitter handles and developers of the app, based on the complaint of a Muslim woman.

But many complaints said the lack of progress on the previous investigations had inspired little confidence.

For years, Ms. Bég has been a vocal critic of India’s governing Hindu nationalists and their anti-minority policies under Mr. Modi. She has faced intense internet trolling, including death threats, on Twitter.

Over the years, as the pressure has intensified, she said, she started self-censoring, avoiding critical posts on the policies of the Hindu nationalists.

She said she had been worried about the rising intolerance, but the latest episode showcased how the online machinery was being used to make vocal Muslim women withdraw from public life, essentially eliminating any counternarrative.

Hasiba Amin, a social media coordinator of the opposition Congress party, who was also featured on the auction app, says the fact that the violence and death threats against minorities online have recently gone beyond virtual is what keeps her awake.

“What guarantees do we have from the government that tomorrow the threats and intimidation online is not going to turn into the real-time sexual violence on the streets?” she asked.