GEOFF BENNETT: Georgia is one of the battlegrounds where local and state officials are grappling with some big changes about certifying the vote and a new requirement to hand-count the total number of ballots.

Miles O'Brien looks at another concern raised by some experts about a potential vulnerability of the voting machines.

State officials say they are more than prepared.

Here's his report.

MILES O'BRIEN: It's a few weeks before a primary Election Day in Bartow County, Georgia, and election workers are conducting a logic and accuracy test of computers that stand between voters and their ballots.

WOMAN: Where it says tech size, touch down and then do big.

MAN: Big, OK.

MILES O'BRIEN: They are ImageCast ballot marking devices, or BMDs, made by Dominion Voting Systems.

Everyone who votes in person in Georgia uses one of these touch screen computers to record their choices and then prints a marked paper ballot, which gets scanned and tabulated.

So are these machines worth the added cost and complexity?

JOSEPH KIRK, Elections Supervisor, Bartow County, Georgia: I advocated for them.

MILES O'BRIEN: Joseph Kirk is the elections supervisor here.

He says the ballot marking devices offer advantages over paper ballots marked by hand.

JOSEPH KIRK: It guides the voter through the process and makes sure that there's no question about their intent.

MILES O'BRIEN: A small percentage of selections on hand-marked ballots are disqualified because voters make ambiguous markings.

Dominion's ballot marking devices may address that issue, but many election security experts say they inject stubborn uncertainties into the voting process.

J. ALEX HALDERMAN, University of Michigan: Fundamentally, it's a problem any time that you're going to put a potentially vulnerable computer between the voter and the only records of their vote.

MILES O'BRIEN: J. Alex Halderman is a professor of electrical engineering and computer science at the University of Michigan.

He is among those who advocate for hand-marked paper ballots.

I guess it seems ironic that the best computer scientists in the world will tell you the best technology for an election is pen and paper.

J. ALEX HALDERMAN: Well, that's absolutely right.

And the reason for that is, we know how paper can be secured and we know how digital systems can be attacked, right?

The risks aren't even comparable.

MILES O'BRIEN: Halderman has spent a lot of time studying the risks.

He is an expert witness for the plaintiffs in a pending federal lawsuit seeking an injunction against using the current voting system.

Halderman says he and his team found nine vulnerabilities in the Dominion system.

We met at a law office in Atlanta in March.

He showed me some of what he demonstrated in open court.

J. ALEX HALDERMAN: We thought like an attacker.

What would an attacker want to do?

How could an attacker circumvent the layers of protection that are in this machine and in a real polling place?

MILES O'BRIEN: Halderman demonstrated a few seemingly easy ways to breach the security of the Dominion ballot marking device.

He used a pen to recycle the power, which gave him administrative control of the computer and he used a widely available USB device favored by computer security experts and hackers to rewrite the software of the machine.

All of this mischief could occur without an obvious trace.

That's because the scanner that tabulates the votes does not look at the human readable text.

Instead, it derives its data from this Q.R.

code.

J. ALEX HALDERMAN: We can change just the Q.R.

code and leave all of the voter visible text identical to what the voter entered on screen.

So, as a voter, there's nothing at all that you can see that's going to indicate there was a problem.

MILES O'BRIEN: Halderman and his team worry that the hacks could propagate through an entire county or even statewide.

While the ballot marking devices are not directly plugged into the Internet, as they are updated and operated, they regularly exchange data with online systems through USB memory sticks and smart cards.

J. ALEX HALDERMAN: That can potentially provide a route for hackers far away on the Internet to gain access to BMDs.

The kinds of attackers that worry me in this scenario include some of the most sophisticated adversaries in the world, foreign governments like Russia or China or Iran.

MILES O'BRIEN: We asked Dominion for a response.

A spokesperson e-mailed us this: "The claim that someone could hack an election with a pen is flatly false.

A court directive gave Mr. Halderman, as plaintiff's paid expert, unfettered access to system security features, including passwords, security cards, election files and more.

This did not take into account the many layers of physical and operational safeguards."

There is no evidence that any of these apparent vulnerabilities have ever been exploited.

Georgia state election officials say they are hypothetical scenarios.

GABRIEL STERLING, Georgia Voting System Implementation Manager: Almost all of these are mitigated by the processes that are put in place around the election system itself.

MILES O'BRIEN: Gabe Sterling is the chief operating and financial officer for the secretary of state.

He says the many layers of people and processes surrounding these machines make it impossible for a voter to reboot them with a pen or insert a USB device without being detected.

So what Alex Halderman demonstrated, you believe, is not a real-world scenario?

GABRIEL STERLING: The computer experts focus solely, solely, solely on the computer.

They focus nothing on voting processes and human behavior, but they don't look at the entirety of how the system works.

The reality of it is, is, there are so many safeguards around it.

MILES O'BRIEN: But what if there was an inside job?

This is exactly what happened in early 2021 in rural Coffee County, Georgia.

The election supervisor and the local chair of the Republican Party invited Trump campaign allies and a data forensics team into the secure area where the Dominion machines and the election management server are stored.

For several days, they copied proprietary software and confidential data.

It is one of the most infamous security breaches in U.S. election history.

It was uncovered by the Coalition for Good Governance and other plaintiffs in that federal lawsuit.

David Cross is one of the lead attorneys.

DAVID CROSS, Plaintiff's Attorney: It was distributed on the Internet to people that have I.P.

addresses that show up around the world.

And so it's hard to know where all this is going at this point.

MILES O'BRIEN: Did they give away all the keys, essentially?

Are they all out there?

DAVID CROSS: Those keys have been out in the ether now for years.

The state has done nothing to protect the system against that.

MILES O'BRIEN: In late 2022, Dominion Voting Systems released a new software system, which makes the Q.R.

code optional.

It was approved by the United States Election Assistance Commission in early 2023.

But Georgia has yet to upgrade its fleet of about 30,000 machines.

BRAD RAFFENSPERGER (R), Georgia Secretary of State: People somehow thought that this was like an iPhone download that you do overnight.

MILES O'BRIEN: Brad Raffensperger is Georgia's secretary of state.

BRAD RAFFENSPERGER: No, this is actually a full deinstallation, a reinstallation of boots on the ground in all 159 counties of all 30,000 pieces of equipment.

MILES O'BRIEN: How much time does it take to do that?

BRAD RAFFENSPERGER: We're looking at four to six months.

MILES O'BRIEN: In early 2023, Raffensperger asked the state legislature for $25 million to get the job done in time for the November 5 presidential election.

But the request was not approved.

You have such a complex system, that it's not able to respond to a security threat very quickly, is it?

BRAD RAFFENSPERGER: Well, we are where we are, and so we are now into an election.

So those are issues that the General Assembly can take up next session, and they don't meet until next January.

MILES O'BRIEN: The state did pass a law to eliminate the Q.R.

codes by 2026.

In the meantime, Georgia is relying on additional oversight to save the day in a contested election.

In addition to the logic and accuracy testing before the machines are deployed, state election workers will conduct parallel monitoring while the machines are in use, which we saw during the presidential primary in March.

They randomly selected BMDs from various counties and tested them for accuracy on Election Day.

MAN: So we know what the county is using matches our control.

MILES O'BRIEN: And after the election, they will conduct risk-limiting audits designed to deliver a statistically valid confirmation of the results.

During those audits, the votes are verified with the human legible text, not the Q.R.

codes.

And if it is as close and contested as in 2020, Georgia is prepared to do a 100 percent hand recount.

If one aspect does, in fact fail, do you feel pretty confident one way or another you will catch it?

BRAD RAFFENSPERGER: Yes.

Our system and our people are battle-tested.

We have been through 2020, we have been through 2022, and we're ready for 2024.

MILES O'BRIEN: Ready or not, Georgians who vote in person this year will use Dominion ballot marking devices.

As voters cast their ballots, political operatives are likely poised to cast doubt on whether the machines can be trusted.

For the "PBS News Hour," I'm Miles O'Brien in Atlanta.