CNN  — 

A phone app that Mike Waltz, President Donald Trump’s former national security adviser, apparently used to save his text messages has temporarily suspended its services as it investigates a cybersecurity incident, a spokesperson for the app’s parent company told CNN on Monday.

TeleMessage, which makes software for preserving and organizing messages sent via Signal and other mobile apps, is responding to a “recent security incident” and has hired an external cybersecurity firm to help investigate, a spokesperson for Oregon-based digital communications firm Smarsh told CNN.

“Out of an abundance of caution, all TeleMessage services have been temporarily suspended. All other Smarsh products and services remain fully operational,” the Smarsh spokesperson said.

The extent of the hack is unclear. A Smarsh spokesperson did not immediately respond to questions about what data, if any, the hackers took. Smarsh acquired Israel-based TeleMessage last year.

404 Media, a tech-focused news outlet, first reported on the hack affecting TeleMessage.

Waltz had been under intense pressure since news broke in March that he had inadvertently added the Atlantic’s editor-in-chief to a Signal chat in which senior members of the Trump administration disclosed sensitive information on a US military strike in Yemen.

A photograph taken by Reuters of Waltz on his phone during a Cabinet meeting Wednesday appeared to show Waltz using TeleMessage. The photo appeared to show chat logs on Waltz’s phone with Vice President JD Vance and Secretary of State Marco Rubio, among others. All three men were in the now-infamous Signal group chat.

CNN has requested comment from the National Security Council on Waltz’s use of TeleMessage.

Trump announced on Thursday that Waltz would be leaving his post as national security adviser to serve as ambassador to the United Nations, pending Senate confirmation.

Joshua Steinman, who served as a top cyber official at the National Security Council in the first Trump term, said the use of TeleMessage, if confirmed, could serve as a “juicy intel target” for foreign powers.

“**If true**, why was the U.S. Government using a foreign built technology (I don’t care which foreign) to capture these messages?” Steinman posted on X on Monday. “Would literally be such a juicy intel target that I just straight up assume it’s being exploited.”