As Waltz faces UN post hearings, an update on the Signal situation that led to his initial ousting

As Mike Waltz, President Donald Trump's nominee for U.S. ambassador to the United Nations, appears before the Senate Foreign Relations Committee Tuesday for his confirmation hearing, focus returns to his ousting as national security adviser over what some referred to as "Signalgate."

The former Florida Republican congressman served mere weeks in Trump's administration before revelations that he mistakenly added journalist Jeffrey Goldberg of The Atlantic to a private Signal chat that was used to discuss sensitive military plans, including planning for strikes on Houthi militants in Yemen.

Calls came quickly for Defense Secretary Pete Hegseth to be removed from office, accompanied by criticism of the Trump administration for failing to take action against the top national security officials who discussed plans for the military strike in Signal. After weeks of scrutiny, Waltz left his security post but was swiftly nominated to the U.N. position.

Months after the chat was disclosed, questions remain over the controversy, including if federal laws were violated, if classified information was exposed on the commercial messaging app and if anyone else will face consequences.

Here’s what we know and don’t know:

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KNOWN: Signal is a publicly available app that provides encrypted communications, but it can be hacked. It is not approved for carrying classified information. On March 14, one day before the strikes, the Defense Department cautioned personnel about the vulnerability of Signal, specifically that Russia was attempting to hack the app, according to a U.S. official who was not authorized to speak to the press and spoke on the condition of anonymity.

One known vulnerability is that a malicious actor, if they have access to a person’s phone, can link their own device to the user’s Signal — and monitor messages remotely.

NOT KNOWN: How frequently the administration and the Defense Department use Signal for sensitive government communications, and whether those on the chat were using unauthorized personal devices to transmit or receive those messages. The department put out an instruction in 2023 restricting what information could be posted on unauthorized and unclassified systems.

At a Senate Intelligence Committee hearing earlier this year, Director of National Intelligence Tulsi Gabbard would not say whether she was accessing the information on her personal phone or government-issued phone, citing an ongoing investigation by the National Security Council.

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KNOWN: The government has a requirement under the Presidential Records Act to archive all of those planning discussions.

NOT KNOWN: Whether anyone in the group archived the messages as required by law to a government server. The images of the text chain posted by The Atlantic show that the messages were set to disappear in one week.

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KNOWN: Hegseth had an internet connection that bypassed the Pentagon's security protocols — known in the IT industry as a "dirty" internet line — set up in his office to use Signal on a personal computer, two people familiar with the line have told The Associated Press.

Other Pentagon offices have used them, particularly if there’s a need to monitor information or websites that would otherwise be blocked. The biggest advantage of using such a line is that the user would not show up as an IP address assigned to the Defense Department — essentially the user is masked, according to a senior U.S. official familiar with military network security.

NOT KNOWN: If use of the line left any Defense-related materials more vulnerable than they would have been on a Pentagon secure line.

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KNOWN: The chat group included 18 members, including Jeffrey Goldberg, top editor of The Atlantic. The group, called “Houthi PC Small Group,” likely for Houthi “principals committee” — was comprised of Trump’s senior-most advisers on national security, including Gabbard, Defense Secretary Pete Hegseth, Secretary of State Marco Rubio and CIA Director John Ratcliffe. The National Security Council said the text chain “appears to be authentic.”

NOT KNOWN: How Goldberg got added. Waltz said he built the message chain and didn’t know how Goldberg ended up on the chat. He called it a mistake.

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KNOWN: Just hours before the attack on the Houthis in Yemen began, Hegseth shared details on the timing, targets, weapons and sequence of strikes that would take place.

NOT KNOWN: Whether the information was classified. Gabbard, Ratcliffe and the White House have all said it was not classified, and Hegseth said the same in a post on social media. Democrats said that strains credulity.

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KNOWN: Hegseth has adamantly denied that "war plans" were texted on Signal, something current and former U.S. officials called "semantics." War plans carry a specific meaning. They often refer to the numbered and highly classified planning documents — sometimes thousands of pages long — that would inform U.S. decisions in case of a major conflict.

But the information Hegseth did post — specific attack details selecting human and weapons storage targets — was a subset of those plans and was likely informed by the same classified intelligence. Posting those details to an unclassified app risked tipping off adversaries of the pending attack and could have put U.S. service members at risk, multiple U.S. officials said.

Sharing that information on a commercial app like Signal in advance of a strike “would be a violation of everything that we’re about,” said former Defense Secretary Chuck Hagel, who served under Democratic President Barack Obama.

NOT KNOWN: If anyone outside the messaging group got access to the Signal texts.

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KNOWN: Hegseth began cracking down on unauthorized leaks of information inside the Defense Department, and his chief of staff issued a memo on March 21 saying the Pentagon would use polygraph tests to determine the sources of recent leaks and prosecute them.

NOT KNOWN: Whether Hegseth will take responsibility for the unauthorized release of national defense information regarding the attack plans on the Houthis. Trump in March bristled at a suggestion that Hegseth should step down, saying “He’s doing a great job. He had nothing to do with it.”

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KNOWN: In April, Dan Caldwell, a senior Hegseth adviser who in the Signal chat had been designated as the secretary's point person, was placed on administrative leave and escorted out of the Pentagon by security. Officials who spoke on condition of anonymity to discuss personnel matters told The AP that the former Marine's sudden downfall was tied to an investigation into unauthorized disclosure of department information.

NOT KNOWN: If any others affiliated with the Signal situation will face reprisals.

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KNOWN: Also in April, Hegseth was forced to defend himself against a second assertion that he shared classified material through an unapproved and unsecured network, this time taking airstrike information from a military communications channel and sharing it in a Signal chat with his wife, his brother and others. A person familiar with the chat confirmed to The AP that Hegseth pulled the information — such as launch times and bomb drop times of U.S. warplanes about to strike Houthi targets in Yemen — he posted in the chat from a secure communications channel used by U.S. Central Command.

NOT KNOWN: If that's the extent of Hegseth's Signal usage.

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KNOWN: The Pentagon's watchdog has begun looking into Hegseth's use of Signal, and also whether any of Hegseth's aides were asked to delete Signal messages that may have shared sensitive military information with a reporter.

NOT KNOWN: What the inspector general will find, or what will be done as a result of those findings.

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Kinnard can be reached at http://x.com/MegKinnardAP.