What is Signal, the Messaging App Used by Trump Officials?

Messaging app Signal is dominating headlines after the White House confirmed senior US officials used it for a secret group chat. 

Atlantic Editor-in-Chief Jeffrey Goldberg was added to the chat, where United States national security officials including Defence Secretary Pete Hegseth and Vice President JD Vance discussed strike plans targeting the Houthi group in Yemen. 

Goldberg published an article on 24 March detailing how he was added to the Signal group, explaining that at first he “didn’t think it could be real”.

The US National Security Council has since said the message chain “appears to be authentic” – the Atlantic published a transcript of the text messages on Wednesday 26 March. 

The use of Signal to allegedly discuss highly sensitive military operations and the inadvertent sharing with Goldberg has raised questions about the app, including around its level of security against malicious actors. 

Democrat Senate leader Chuck Schumer said the episode is “one of the most stunning” military intelligence leaks in history. 

But what is Signal and is it a secure enough platform for government members and politicians to use?

Signal: Privacy-focused communication

Signal is a free, open-source messaging app launched in 2014 and used by an estimated 40-70 million people per month – a relatively small number compared to other messaging platforms like WhatsApp.

It was built with security in mind, and is renowned for its approach to privacy and providing users the ability to “speak freely”.  

While not as large in terms of user base, the app has found favour with journalists, activists, government officials and anyone else seeking a secure means of communication.  

Signal enables users to send text and voice messages, make voice and video calls, and share photos, videos, GIFs and files.

It supports both one-on-one conversations and group chats, accommodating up to 1,000 participants. A key security-related feature is the option to set messages to disappear automatically after a specified period, thus enhancing privacy and control over shared information. 

Security and data privacy

Signal uses end-to-end encryption, powered by its one open-source Signal Protocol, to keep conversations safe. Neither the company or other users can read messages or listen to calls, and the app features no advertising or affiliate marketers to boost security posture. 

Signal’s security protocol is widely considered an industry standard and is also utilised by other platforms like WhatsApp. 

In addition, unlike some messaging apps, Signal's encryption is enabled by default, providing users with inherent security without requiring additional configuration. 

Signal adheres to a strict "no data collection" policy. It doesn’t store or collect sensitive user information, including message content, call logs or contact lists. This ‘data minimisation’ approach is designed to significantly reduce the risk of user data being compromised or misused.

In a post on X after the US story became public, Signal President Meredith Whittaker said the app “is the gold standard in private comms”.

Meredith added: “We’re open source, nonprofit and we develop and apply e2ee and privacy preserving tech across our system to protect metadata and message contents.”

Previous security concerns

On 25 March CBS News reported that the US National Security Agency (NSA) had sent a previous operational security bulletin to employees in February 2025, warning them of vulnerabilities in Signal.

CBS says it was provided with unclassified but for-official-use-only documents by a senior US Intelligence official. Entitled "Signal Vulnerability”. 

It says these highlight that Signal is used by "common targets of surveillance and espionage activity”, making it a “high value target to intercept sensitive information”.

According to CBS, the bulletin warned of Russian hacking activity related to the app and said that NSA employees were not permitted to use it or other messaging applications for communicating sensitive information. 

The investigation into senior officials’ use of Signal is ongoing.

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