AMNA NAWAZ: A blue check mark on Twitter used to be a way for users to verify the authenticity of an account.

But, recently, CEO Elon Musk said people must pay $8 a month for the platform's -- quote -- "Twitter Blue subscription service."

As a result, journalists, politicians, celebrities, city and government organizations who would not pay have been stripped of their verified status, causing chaos and confusion about what information can be trusted.

I'm joined now by Juliette Kayyem.

She's professor at the Harvard Kennedy School of Government and former assistant secretary at the Department of Homeland Security.

Julie, it's good to have you here.

JULIETTE KAYYEM, Former Department of Homeland Security Assistant Secretary: Thank you.

Thanks for having me.

AMNA NAWAZ: So, to get a blue check previously, there was a process.

You had to have your identity verified.

Like many journalists, I had one as well.

What are the real-world implications of that verification process going away?

JULIETTE KAYYEM: So, verification was part of an overall process that Twitter had that made it the most reliable platform in - - especially in times of emergency or disaster, which is the world that I come from, disaster management.

And what it did is, it ensured that the way the algorithm worked is that, when something bad happened, journalists, government officials, emergency managers, their information, what they were seeing, what they were hearing, and, most importantly, what did they want community members to do, do you run, do you hide, do you evacuate, do you shelter in place -- those are important decisions to be made with just a few moments' notice.

All of those were now valid -- were validated through the blue check mark.

Now, just based on experience, but because we know the blue check mark is unreliable, Twitter feeds -- just think of a school shooting.

Twitter feeds are just unreliable.

They're not helpful.

They're not giving you information in real time.

So that has been a -- I use -- I said, Twitter used to be good at saving lives.

I know it's hard for people to believe, but it really became a way in which public safety agencies were pushing out information.

And, as importantly, it became a way in which communities and information was being heard by government officials.

That's a system with -- that's called API, but, basically, in, let's say, the earthquake in Turkey... AMNA NAWAZ: Yes.

JULIETTE KAYYEM: ... government officials would follow what was happening on Twitter.

There's a lot of people who seem to be under rubble here.

There's a lot of people who seem to be without water here.

And that would help drive resources.

That whole system is now unreliable and not accessible.

And so I know we talk a lot about what's bad about Twitter.

But, at one stage, it was really good.

It was really, really good.

There's the emergency and disaster response part of it.

There's also the misinformation part of it.

AMNA NAWAZ: What are sort of the worst-case consequences you're seeing?

JULIETTE KAYYEM: Well, we saw it -- we saw it on day one when the blue check mark could be bought.

Someone clever, not -- it didn't seem like he was nefarious -- bought the National Weather Service name, so that... JULIETTE KAYYEM: ... if you were looking for the National Weather Service, which is the sort of best assessor of what weather is telling us... JULIETTE KAYYEM: ... and then it's pushing out information based on where you are regionally or locally, someone bought the check mark, so that if you went to National Weather Service, you might be watching that.

Now we're seeing it in terms of New York -- like, for example, New York City services, emergency management entities.

(CROSSTALK) AMNA NAWAZ: These are fake accounts, basically, that paid for a check mark, right?

JULIETTE KAYYEM: Fake accounts that are -- and it's -- and in a disaster, time is really your most valued commodity.

JULIETTE KAYYEM: And Twitter was really good at sort of pushing out information in real time very quickly, very reliably.

JULIETTE KAYYEM: And there's -- and they liked it.

I mean, that's the interesting thing.

If you go back to the company -- and I have worked with the company over years.

They really thought that this was a role that was important to them as a company.

And then that's all been abandoned.

AMNA NAWAZ: What about Elon Musk's approach to journalists and to journalism, writ large?

AMNA NAWAZ: And for folks who haven't been tracking this, we should also say, in the interest of full disclosure, our PBS "NewsHour" account still does tweet out our reporting and information.

But Musk had stripped The New York Times of their verified status.

He tweeted that: "The real tragedy of The New York Times is their propaganda isn't even interesting."

That's to his 137 million followers.

He's also suspended accounts of journalists who follow him.

He added a state-affiliated media label to NPR's account.

JULIETTE KAYYEM: Yes.

AMNA NAWAZ: I mean, what message does that send?

JULIETTE KAYYEM: So, he's basically trolling journalists, because the journalists are critical of him or their - - just the reporting is critical of him.

And he seems to now view Twitter as sort of his own sort of hit list, I guess I would say, that he's using it as a way to make it impossible for legitimate journalists, for legitimate institutions to get out information, legitimate information in real time.

Will he stop doing that?

One hopes.

I always think that he's just going to -- he seems like someone who will get bored with this and then move on to the next thing.

But there's legitimate damage being done, one, because it misrepresents some journalists and what they're doing, and may elevate other journalists.

There's people who should not, for example, be called journalists.

JULIETTE KAYYEM: And, also, it undermines the legitimacy of organizations like PBS or NPR.

AMNA NAWAZ: I need to ask you in the minute or so we have left about a story we reported on earlier... AMNA NAWAZ: ... the revelations around Jack Teixeira, that Massachusetts Air National Guardsman accused of leaking those intelligence documents.

In a previous role... AMNA NAWAZ: ... you oversaw the Massachusetts Air National Guard.

AMNA NAWAZ: And I just wonder how you are taking all of this in about how someone like that got a security clearance?

It seems inconceivable, until I tell you that 1.3 million people have top secret clearance.

It's just -- it's too many people at this stage.

And as a public and private, that's -- it's national, federal, state.

It's -- lots of people have access to classified information.

And it seems where the gap was -- or there are two gaps here.

One was, he was doing all sorts of things when he was 16 and 17 years old, not good things at all.

I think that's racism, threatening people.

And, somehow, the Pentagon cleared him, sort of excused it as sort of youthful transgressions, and we're going to -- we're going to let him in.

But, once they do that, they then give him access to everything.

And I think that the question now is, it's inconceivable to me that he had access to everything that he was then able to release.

So there's the question of, how did he get it in the first place?

Why did he have access for this particular job?

And then the question that the Pentagon is going to have to answer, over months, he is putting this stuff online, and no one at the Pentagon captures it.

He's putting it on gaming platforms for months.

AMNA NAWAZ: Still a lot of questions.

JULIETTE KAYYEM: A lot of questions.

AMNA NAWAZ: Juliette Kayyem, professor at the Harvard Kennedy School of Government, thank you for being here.

JULIETTE KAYYEM: Thanks for having me.