Pentagon issued Signal warning before war group chat leak: Report

• Pentagon officials issued a warning about vulnerabilities in the Signal messaging app. It cited Russian hacking groups exploiting the “linked devices” feature to spy on encrypted conversations.
• Signal responded, clarifying that the memo was not about the app’s security but to alert users about phishing threats.
• The Pentagon memo emphasized that while Signal is permitted for certain unclassified uses, it is not approved for processing nonpublic unclassified information.

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Pentagon officials issued a warning about the use of the Signal messaging app just days before the Atlantic published its editor-in-chief, Jeffrey Goldberg, had been mistakenly added to a group chat where high-ranking officials discussed military plans.

That’s according to a department-wide email from March 18, obtained by NPR.

What was in the memo?

The memo stated, “A vulnerability has been identified in the signal messenger application.”

It went on to say, “Russian professional hacking groups are employing the ‘linked devices’ features to spy on encrypted conversations.”

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A Signal spokesperson told NPR the Pentagon memo is not about the messaging app’s level of security. Instead, the Pentagon said the memo alerted Signal users to be aware of hackers.

“Once we learned that signal users were being targeted and how they were being targeted, we introduced additional safeguards and in-app warnings to help protect people from falling victim to phishing attacks. This work was completed months ago,” Signal spokesman Jun Harada said.

The Pentagon memo added, “Please note: third party messaging apps (e.g. Signal) are permitted by policy for unclassified accountability/recall exercises but are not approved to process or store nonpublic unclassified information.”

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How did officials use Signal in this case?

The encrypted Signal app is what Defense Secretary Pete Hegseth and other Trump administration officials, including Vice President JD Vance and Director of National Intelligence Tulsi Gabbard, used to discuss bombing Houthi sites this month. 

Gabbard testified this week before the House Intelligence Committee that the conversation on signal remained “candid” and “sensitive,” but no one shared classified information. 

A spokesperson for the National Security Council said the administration was reviewing how Goldberg’s number was added to the group chat.