Sam Schechner and Robert McMillan

Meredith Whittaker spent her first few years running Signal preaching the encrypted-messaging app's benefits for sensitive conversations, regardless of whether users had anything to hide.

This week her pitch got a lot easier. Signal attracted a wave of users after the Atlantic published the details of a group chat in which Defense Secretary Pete Hegseth shared war plans with a group that included key members of the Trump administration, including the vice president, as well as the magazine's editor in chief.

Signal said app downloads this week are double what they were last week. Suddenly, the not-for-profit app that competes with Meta Platforms's WhatsApp and Apple's iMessage with a paltry $50 million annual budget is ascendant.

"Every time there is what we call a big tech screw-up or a massive data breach, we see spikes in Signal growth," Whittaker said in an interview last fall with the podcaster Kara Swisher. Whittaker declined to comment for this article.

Signal co-founder Moxie Marlinspike, a hacker with anarchist leanings, this week reflected on the app's transition from a privacy passion project to a tool trusted by dissidents, journalists, spies and Washington's elite.

"There are so many great reasons to be on Signal," he said on X. "Now including the opportunity for the vice president of the United States of America to randomly add you to a group chat for coordination of sensitive military operations."

The app, which now has 30 million monthly users, collects virtually no user data and makes it difficult to discover others on Signal, making a viral Signal post a near-impossibility. Whittaker has touted its privacy and security over that of rival apps and said it exists to help the masses, not any one group or cause.

"We are really laser-focused on the mission of maintaining a meaningful way to communicate intimately and privately with the people we care about in a world where that is decreasingly possible," she said in an interview with The Wall Street Journal at the World Economic Forum in Davos, Switzerland, last year.

Funded by donations and grants to cover expenses such as bandwidth and hosting, Signal got its start as a messaging service hatched by a self-described crypto enthusiast.

When Marlinspike -- an alias -- first proposed the software that would become Signal, it was his way of striking a blow against the surveillance powers of government and big business.

Marlinspike laid out the struggle to preserve privacy in 2010, while speaking to a room full of hackers at a Las Vegas conference. The fight, he said, pitted data-collecting entities such as Google and the government against "cypherpunks" -- the pro-privacy hackers and cryptographers who wanted to be online and anonymous at the same time.

"What cypherpunks wanted was actual software that people could download and use right now so that people could communicate securely," he said.

After a brief stint at Twitter early in his career, Marlinspike merged his texting and voice software into a new app in 2014, calling it Signal. He funded its development with a hodgepodge of grants and donations.

A year later, Signal got its first big endorsement when National Security Agency leaker Edward Snowden said Signal could help thwart government surveillance. In 2016, James Clapper, then U.S. director of national intelligence, told journalists that Snowden had sped up adoption of encryption by seven years.

Scaling up from a small project into a global app grew expensive. The foundation that runs the app reported $5.1 million in expenses in 2018, once it became a nonprofit. The company now spends roughly $50 million a year, according to Whittaker.

Whittaker, who studied literature and has described herself as an art-school kid, left Google in 2019 after organizing protests against its business practices and contracts with the Defense Department. She has been critical of big technology companies' focus on selling ads and social media, and an evangelist for Signal's privacy and simplicity: encrypted messaging in a crisp, ad-free app.

She joined the Signal Foundation board in 2020 and became president of the foundation in 2022, taking over day-to-day operations from Marlinspike. Since then, she has encouraged parents, spouses, friend groups and advocates to shift their communications there.

Much of Signal's current operating costs are for infrastructure, renting servers and hardware from big tech companies such as Amazon Web Services, Google and Microsoft.

WhatsApp co-founder and Signal foundation Executive Chairman Brian Acton has lent the foundation a total of more than $105 million, according to the foundation's most recent federal nonprofit filing.

Signal has capitalized on key moments over the past decade to surge in popularity as a default choice for digital gabbing, endorsed by figures from Elon Musk to the organizers of the Black Lives Matter movement.

Signal was able to grow from a hacker project to a global communication network in part because it makes its encryption software open-source, building trust over time with security-conscious users, Whittaker said this month during an interview at the SXSW conference in Austin, Texas. She said Signal also works hard to make its app useful for people who don't care much about privacy -- creating a network effect that couldn't easily be rebuilt.

"I feel sometimes like a dragon outside a cave, just protecting this jewel that we have," she said. "We have to sustain it."

Write to Sam Schechner at Sam.Schechner@wsj.com and Robert McMillan at robert.mcmillan@wsj.com

(END) Dow Jones Newswires

March 27, 2025 20:00 ET (00:00 GMT)

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