Neeraj Agrawal, a spokesperson for a think tank for cryptocurrency, has typically used the encrypted messaging app Signal to chat with privacy-conscious colleagues and colleagues. He was surprised on Monday when the app drew his attention to two new users: mom and dad.

“Signal still had a subversive glow,” said Mr. Agrawal, 32. “Now my parents are in.”

Gavin McInnes, founder of the far-right Proud Boys group, had just announced his return on Telegram. “Man, I haven’t posted anything here in a while,” he wrote on Sunday. “I will post regularly.”

And on Twitter, Elon Musk, the billionaire entrepreneur, also weighed in two words last week: “Use Signal”.

In the past week, tens of millions of people downloaded Signal and Telegram, making them the two hottest apps in the world. With Signal, messages can be sent with “end-to-end encryption”, ie only the sender and recipient can read the content. Telegram offers some encrypted messaging options, but is mostly popular for its group-based chat rooms where users can discuss a wide variety of topics.

Their sudden surge in popularity was fueled by a series of events over the past week that raised concerns about some of the big tech companies and their communication apps, like WhatsApp, which Facebook owns. Tech companies like Facebook and Twitter removed thousands of far-right accounts – including President Trump’s – after the Capitol storm. Amazon, Apple, and Google have also dropped support for Parler, a social network popular with Mr. Trump’s fans. In response, conservatives looked for new apps to communicate with.

At the same time, privacy concerns about WhatsApp were mounting, which last week a pop-up notification reminded users that some of their data will be shared with the parent company. The notification sparked a wave of fear fueled by viral chain messages falsely claiming Facebook could read WhatsApp messages.

The result has been mass migration that, if it continues, could weaken the power of Facebook and other big tech companies. On Tuesday, Telegram announced that it had added more than 25 million users in the past three days, which equates to more than 500 million users. According to estimates by Apptopia, an app data company, Signal added nearly 1.3 million users on Monday alone, after an average of just 50,000 downloads per day last year.

“We already had a lot of downloads,” said Pavel Durov, CEO of Telegram, in a message on the app on Tuesday. “But this time it’s different.”

Carl Woog, a spokesman for WhatsApp, said that users’ privacy settings have not changed and that rumors about what data is being shared are largely unfounded.

“What doesn’t change is that private messages to friends and family, including group chats, are protected with end-to-end encryption so that we can’t see them,” he said.

The rise of Telegram and Signal could spark the debate about encryption, which helps protect the privacy of people’s digital communications, but can hinder authorities in criminal investigations as conversations are hidden.

In particular, the move to apps by far-right groups has worried US authorities, some of whom are trying to track plans for potentially violent rallies at or before the inauguration of President-elect Joseph R. Biden Jr. next week.

“The proliferation of encrypted platforms where law enforcement can’t even monitor rhetoric enables groups with bad intent to plan behind the curtain,” said Louis Grever, director of the Association of State Criminal Investigative Agencies.

Capitol Riot Fallout

Updated

Jan. 13, 2021, 9:36 p.m. ET

Telegram is particularly popular with right-wing extremists as it mimics social media. After Facebook and Twitter limited Mr Trump to their services last week and other companies enlisted their assistance from Parler, right-wing groups on Parler and other fringe social networks posted links to new Telegram channels and encouraged people to join them.

In the four hours after Parler went offline on Monday, a Proud Boys group on Telegram gained over 4,000 new followers.

“Don’t trust Big Tech,” read a message in a Proud Boys group on Parler. “We need to find safer rooms.”

On Signal, a Florida-based militia group said Monday that it is organizing its chats in small city-to-city chats, limited to a few dozen people each, according to the New York Times. They warned each other not to let in anyone they did not know personally to avoid police officers spying on their chats.

The deluge of users of Telegram, based in Dubai, and Signal, based in Silicon Valley, goes well beyond American right. Mr Durov said 94 percent of Telegram’s 25 million new users were from Asia, Europe, Latin America, the Middle East and North Africa.

The majority of Signal’s new users are from outside the United States. As of Wednesday, the company announced that it was the # 1 app in 70 countries on iOS devices and 45 countries on Android devices, with India being one of the biggest areas for new user growth. For both Signal and Telegram, new installations came from users in Indonesia, Mexico, Brazil and dozens of other countries, data from Apptopia shows.

Concerns about WhatsApp’s privacy policy have increased Telegram and Signal’s popularity. While there haven’t been any significant changes to the way WhatsApp handles user data, users immediately interpreted the app’s privacy notice last week as infiltrating and infiltrating all kinds of personal information – such as personal chat logs and voice calls passes this data on to companies.

WhatsApp was quick to say that people were wrong and that it couldn’t see anything in encrypted chats and calls. But it was too late.

“The whole world now seems to understand that Facebook doesn’t create apps for them, Facebook apps for their data,” said Moxie Marlinspike, Founder and CEO of Signal. “It took this one little catalyst to get everyone over the edge of change.”

The passion was so great that Moses Tsali, a rapper from Los Angeles, released a music video for his song “Hit Me On Signal” on Tuesday. And Mr. Musk’s endorsement of Signal last week drove publicly traded shares of Signal Advance Inc., a small medical device maker, from a market value of around $ 50 million to over $ 3 billion. (The company has no relationship with the messaging app.)

Some world leaders have also urged people to join them on the apps. On Sunday, President Andrés Manuel López Obrador’s Twitter account from Mexico spoke about his new telegram group. As of Wednesday, it had nearly 100,000 members.

Eli Sapir, executive director of Apptopia, said that while WhatsApp has fairer concerns about data collection on Facebook, WhatsApp actually uses more secure encryption than Telegram. “It’s like switching from something high in sugar to corn syrup,” he said, adding that Signal was the safest of the three.

Meyi Alabi, 18, a student in Ibadan, Nigeria, said she was surprised this week when her mother invited her to join Signal. Her mother downloaded the app at the urging of a friend who was worried about WhatsApp.

“I was shocked because she got it before me,” she said. “We usually tell our parents about the new apps. Now we are suddenly informed. “

Mr Agrawal, the cryptocurrency worker, said his parents had long been active in several WhatsApp group chats with college friends and relatives in India. He said they told him they joined Signal to follow many of the chats that moved there because some of the attendees were concerned about WhatsApp’s new policy.

He said he knew the dangers of the WhatsApp policy were overstated, but that much of the public did not understand how their data was being handled.

“They hear these important things – data sharing, Facebook, data protection,” said Agrawal, “and that’s enough for them to say I have to get away from it.”