On TikTok and YouTube, videos claiming voter fraud in Brazil’s recent elections have been recirculating for days.
On the WhatsApp and Telegram messaging services, an image of a poster announcing the date, time and location of the protests against the government was copied and shared over the weekend.
And on Facebook and Twitter, hashtags designed to evade detection by the authorities were used by organizers as they descended onto government buildings in the capital, Brasília, on Sunday.
One day after the thousands of people broke into government buildings to protest what they falsely claim was a stolen election, misinformation researchers are studying how the internet was used to stoke anger and to organize far-right groups ahead of the riots. Many are drawing a comparison to the Jan. 6 protests two years ago in the United States, where thousands broke into the Capitol building in Washington. In both cases, they say, a playbook was used in which online groups, chats and social media sites played a central role.
“Digital platforms were fundamental not only in the extreme right-wing domestic terrorism on Sunday, but also in the entire long process of online radicalization over the last 10 years in Brazil,” said Michele Prado, an independent researcher who studies digital movements and the Brazilian far right.
She said that calls for violence have been “increasing exponentially from the last week of December.”
She and other misinformation researchers have singled out Twitter and Telegram as playing a central role in organizing protests. In posts on Brazilian Telegram channels viewed by The New York Times, there were open calls for violence against the left-wing Brazilian politicians and their families. There were also addresses of government offices for protesters to attack.
In one image, which The Times found on more than a dozen Telegram channels, there was a call for “patriots” to gather in Brasília on Sunday to “mark a new day” of independence. Underneath many of the posters were details of gathering times for protesters.
The hashtag “Festa da Selma” was also widely spread on Twitter, including by far-right extremists who had previously been banned from the platform, Ms. Prado said.
In the months since Elon Musk took over Twitter, far-right figures from around the world have had their accounts reinstated as a general amnesty unless they violated rules again.
Ms. Prado said that misinformation researchers in Brazil have been reporting the accounts to Twitter in hopes that the company takes action.
Twitter and Telegram did not respond to requests for comment.
Meta, the parent company of Facebook, Instagram and WhatsApp, said that the attacks Sunday were a “violating event” and that the company was removing content on its platforms that supported or praised the attacks on government buildings in Brazil.
The protesters in Brazil and those in the United States were inspired by the same extremist ideas and conspiracy theories and were both radicalized online, Ms. Prado said. In both cases, she added, social media played a crucial role in organizing violent attacks.