What is Signal, app used in Yemen war plans chat?

(The Hill) – Top Trump administration officials were revealed this week to have been using digital messaging app Signal to communicate sensitive details about an impending military strike against Houthi terrorists in Yemen earlier this month.

Jeffrey Goldberg, editor in chief of The Atlantic, reported Monday that he had been inadvertently included in a text chain through the encrypted messaging app where Vice President Vance, national security adviser Mike Waltz, Defense Secretary Pete Hegseth and others laid out detailed plans for the attack hours before it took place.

It's unclear what led to Goldberg, a long-time foreign affairs correspondent, being included on the chain. But top administration officials' use of Signal to conduct confidential military discussions has sparked interest in the app and its use in communicating sensitive information.

Signal is considered one of the most secure messaging services because its encryption system blocks third-party access to information about users' private conversations. It is frequently used by journalists, cybersecurity experts, and government officials, among others.

A former national security official told The Associated Press that Signal was used sparingly during the Biden administration and most commonly to notify someone that they needed to check classified information that had been sent through more secure channels.

The communication app, which facilitates group chats among up to 1,000 people and calls with as many as eight people at once, was created more than a decade ago. It is not affiliated with any government and is funded by donations through a nonprofit foundation.

Conversations over Signal are only stored on users' devices, unlike other messaging services from private Big Tech companies, such as Microsoft's Skype and Meta's WhatsApp, that maintain some information on their servers, which can be subpoenaed in legal cases.

Signal has been championed by privacy and tech advocates, including billionaire Elon Musk, who is a top adviser to President Trump, because of its extensive encryption features.

But information can be exposed, as in the airstrike conversation, when a user is mistakenly the recipient of messages or when a personal device is compromised.

When users set up Signal on their cellphones, they are able to sync their contacts to include phone numbers associated with existing Signal accounts.

Goldberg said he received an unsolicited connection invitation appearing to be from Waltz, a former Florida congressman, a few days before he was included on the group text chain about the looming military airstrike. Goldberg said he initially suspected that the discussion and contacts could be part of an elaborate hoax, until the attack took place and White House national security spokesman Brian Hughes confirmed its authenticity.

Signal updated its user interface last year to no longer display users' phone numbers by default.

“This means that when you participate in group chats, message people 1-1, and make Signal calls, your phone number won’t show up unless the person has it saved,” Signal’s developers wrote in a blog post about the change.

According to Goldberg, he appears by his initials “JG” to other users.

Signal also allows users the option to automatically erase messages from their devices and the devices to which they were sent after a set period of time. Goldberg said some messages in the national security thread were set to disappear after a week or four weeks.

The AP reported earlier this month that a detailed review found the app and similar secure messaging services are widely used by government officials across the country, possibly skirting open records laws.