MARY LOUISE KELLY, HOST:

You might want to exercise a little caution should you get a voicemail from a guy who sounds like this.

(SOUNDBITE OF ARCHIVED RECORDING)

MARCO RUBIO: Intelligence leaks are one of the most frustrating things anywhere, not just because you've got somebody...

KELLY: You might also want to exercise caution if you get a text message from the address marco.rubio@state.gov. That is because for the last month or so, an impostor pretending to be the secretary of state has been contacting foreign dignitaries and others using AI software that mimics Marco Rubio's voice and writing style. John Hudson is one of the reporters who broke this story for The Washington Post. He's in our studios now. John, welcome.

JOHN HUDSON: Hey. Great to be with you.

KELLY: How did you stumble on this?

HUDSON: Yeah, so we obtained a cable - my colleague Hannah Natanson and I - that laid out this warning, and the warning was specifically directed at other State Department staffer, saying, if you have any information, if you pick up any instances of someone impersonating the secretary of state, please let us know, direct it to the Bureau of Diplomatic Security.

KELLY: So an internal State Department cable that you all managed to get your hands on?

HUDSON: Yes, exactly. And that's what spelled out originally what U.S. authorities learned, which was, we don't know who this person is, but sometime around mid-June they opened up a Signal account under the name marco.rubio@state.gov, which is not his actual email, but it would...

KELLY: (Laughter) Should we be tempted to write him.

HUDSON: Yes, should you be tempted to send him a love letter or a note of criticism, whatever it may be. And that person, the impostor, began reaching out to very high-level officials - a U.S. governor, a U.S. lawmaker, three foreign ministers - and then began sending these people voice messages, text messages.

KELLY: And do we know if this is over, or is impostor Rubio still out there wreaking havoc?

HUDSON: The person remains unknown. And in the meantime, what they told me is they're taking steps to try to warn people not to fall for this. And obviously, when you talk to information security experts, you know, one of the first lessons is, do not use the encrypted Signal app for government business.

KELLY: So I'm thinking of a couple of things - one, that the real Marco Rubio may be having trouble getting his emails returned if (laughter) everybody's reluctant to respond. Secondly, how hard would this be to pull off? There are a whole lot of samples of Marco Rubio's real voice out there if you want to try to replicate it and send a fake message.

HUDSON: That's a great point. And all you really need is about 15 seconds of audio, and you can upload this into a readily available - there's multiple services that do this, that you upload the audio and then they are able to create an AI version of Marco Rubio's voice, or any other public figure's voice. And then you can just type in and have that voice say whatever you want it to. This is sort of a snapshot into the brave new world that we're in, where this technology allows fraudsters and impostors a huge step and a huge advantage should they want to use the technology for nefarious reasons.

KELLY: These messages were sent over text messaging. These messages were sent over Signal. I can't be the only person listening to and remembering Signalgate, the huge scandal back in March, when then-National Security Adviser Mike Waltz added a journalist, Jeff Goldberg of The Atlantic, to a Signal chat about live U.S. attack plans in Yemen. Mike Waltz ended up out of a job. Marco Rubio ended up getting that job, so he's now national security adviser and secretary of state. My question - does this imposter episode tell us anything about the Trump administration's use of Signal and other nongovernment platforms?

HUDSON: Well, the Trump administration does use Signal extensively. Now, it has started curtailing the use of Signal for extremely sensitive conversations involving groups of national security figures, like what happened in Signalgate. But very senior national security officials continue to use Signal, and now it's known in the public since that incident happened that officials are using Signal, and so...

KELLY: So it makes it more plausible if you get a message from somebody purporting to be Marco Rubio.

HUDSON: One hundred percent.

KELLY: You might think, yeah, he's on there. We know he is.

HUDSON: Absolutely. It's a known conduit for U.S. administration's communications.

KELLY: That's John Hudson. Or at least we think it is.

HUDSON: (Laughter).

KELLY: John Hudson - he covers the State Department and national security for The Washington Post. Thank you.

HUDSON: Thanks, Mary Louise. Transcript provided by NPR, Copyright NPR.

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