'Signal' app prized by activists central to Houthi chat uproar

The messaging app Signal that Trump administration officials used to discuss an attack on Yemen’s Houthi rebels was created by a one-time anarchist to help activists, journalists and others communicate beyond the prying eyes of government intelligence agencies — not to plan government military operations.

Launched by American cryptographer Moxie Marlinspike in 2014, Signal relies on strong end-to-end encryption to ensure users’ privacy and does not save information about the messages it handles. Those features have boosted its popularity among those seeking to evade government or corporate surveillance and cemented Signal’s reputation as the most secure chat app on the market.

Government officials are known to use Signal, too, for communicating among themselves and sometimes to send reporters an occasional news tip. But even with its enhanced security, the app remains off-limits for U.S. officials to exchange sensitive or classified information.

Those restrictions failed to stop top officials in President Donald Trump’s administration from using the app to discuss plans for a military strike in Yemen. On Monday, the Atlantic reported that Defense Secretary Pete Hegseth, Vice President JD Vance and National Security Advisor Mike Waltz earlier this month participated in a Signal group to discuss the Houthi attack. The group was uncovered when one of the officials mistakenly added Atlantic editor Jeffrey Goldberg to it.

Revelations of the breach and the use of an unauthorized platform to exchange sensitive information sent shock waves through Washington, with security experts cautioning that Signal wasn’t an appropriate platform for discussing highly sensitive government information.

“This was a significant operational security failure and should be review closely,” said Mark Montgomery, a retired rear admiral and senior director of the Center on Cyber and Technology Innovation at the Foundation for Defense of Democracies. “Signal is not a secure platform for classified government information.”

At a hearing of the Senate Intelligence Committee on Tuesday, senators from both parties berated Central Intelligence Director John Ratcliffe and Director of National Intelligence Tulsi Gabbard over the episode.

Ratcliffe and Gabbard, who were participants in the Signal chat, defended their role and denied that the information they discussed was classified. But in his article published Monday, Goldberg said that Hegseth texted the group the attack plan that included “precise information about weapons packages, targets and timing.”

The panel’s top Democrat, Senator Mark Warner, expressed exasperation over the incident. “It’s just mind-boggling to me that all these senior folks were on this line and nobody bothered to check, security hygiene 101, who are all the names, who are they?”

Trump said on Tuesday that his administration was investigating the addition of a journalist to the text group. But he said he didn’t think the disclosures warranted a criminal investigation or a directive banning the use of the encrypted messaging app.

“I don’t know anything about Signal,” he said. “I wasn’t involved in this, but I just heard about it, and I hear it’s used by a lot of groups — it’s used by the media, a lot. It’s used by a lot of the military. And I think successfully, but sometimes somebody can get onto those things.”

Mobile devices infected with spyware can allow hackers to read messages, even on Signal, according to James Lewis, senior vice president at the Center for Strategic and International Studies. One of the secrets of espionage, Lewis added, is that people tend to be lazy and take shortcuts. “That’s how you get them,” he said.

“People will tell you that Signal is safe to use, but if you are in the White House or DoD, you have better options,” Lewis said.

National security and intelligence officials are required to use secured, government-issued devices for communications involving classified information. Typically, those discussions involve only individuals with proper security clearances and take place in a sensitive compartmented information facility, or SCIF, which blocks any outside electronic or cellular interference to additionally monitor and control access.

The U.S. government uses its own standalone systems for sharing sensitive information, especially involving potential military operations or other covert actions. Those platforms include SIPRNET, a network for sharing secrets between the State Department and the Defense Department.

“If this was the case of a military officer or an intelligence officer and they had this kind of behavior, they would be fired,” Warner said.

At the Defense Department, rules specifically bar sensitive information from social messaging platforms. Guidance released by the Pentagon in October 2023 stressed that those apps were “NOT authorized to access, transmit, process non-public Defense Department information. This includes but is not limited to messaging, gaming, and social media apps. (i.e., iMessage, WhatsApp, Signal).”

The uproar has shined a light on Signal, a long time bastion for government dissidents and investigative journalists. The app, with fewer than 100 million active users, is a relatively small player in the messaging industry when compared to the likes of WhatsApp and its two billion users.

A representative for Signal didn’t immediately respond to a request for comment. Marlinspike, who stepped down as Signal’s chief executive officer in 2022, also didn’t respond to an email seeking comment.

Part of Signal’s appeal is that it is run by a nonprofit, relying in part on contributions from users, and it has cast itself as an alternative to other messaging apps that collect data on users for advertising and profit. WhatsApp co-founder Brian Acton invested $50 million in 2018 to create the nonprofit corporation Signal Technology Foundation along with Marlinspike. Other backers include Twitter co-founder Jack Dorsey, who has said he would give $1 million a year to keep the service running.

In a post Monday on X, Marlinspike quipped, “There are so many great reasons to be on Signal. Now including the opportunity for the vice president of the United States to randomly add you to a group chat for coordination of sensitive military operations. Don’t sleep on this opportunity.”

Trump on Tuesday sought to defend the officials involved and said the mishap was “the only glitch in two months.” He also expressed support for Waltz, who had apparently included Goldberg in the Signal chat, according to the Atlantic. Gabbard said the White House National Security Council was reviewing “all aspects” of the episode.

Republican Senator Kevin Cramer of North Dakota, a Trump ally, called the blunder an embarrassment. He said he uses Signal for sensitive communications but not classified information.

“I don’t know if a head will roll or has to roll yet, but this has got to be the last time something this big and dumb happens,” Cramer told reporters.

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(With assistance from Steven T. Dennis and Natalia Drozdiak.)

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