On March 18, several days before top national security officials accidentally included a reporter in a Signal chat about bombing Houthi sites in Yemen, the Pentagon issued a warning about using the messaging app, even for unclassified information.
The warning, sent to all Pentagon employees, said, “A vulnerability has been identified in the Signal messenger application.” The email, first reported by NPR, also mentioned that Russian hackers were using the app’s “linked devices” feature to spy on private conversations.
The Pentagon also noted that Google had found Russian hacker groups targeting Signal Messenger to gather information from people of interest.
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 non-public unclassified information.”
The Signal app was used by Defense Secretary Pete Hegseth and other high-ranking officials to discuss military plans earlier this month. However, Atlantic editor Jeffrey Goldberg was accidentally added to the chat, gaining access to these sensitive discussions.
In the military, sharing classified information over unsecured channels is known as “spillage,” and it can lead to severe consequences for the officers involved.
A 2023 memo from the Department of Defense had already banned the use of mobile apps for even “controlled unclassified information,” which is less sensitive than active military operations.
It is rare for top officials from the Defense, State, Intelligence, and National Security sectors to share such sensitive information in an insecure forum.
