Richard Watkins prepares to fill out an absentee ballot at Courthouse Plaza on Oct. 17 in Arlington. (Matt McClain/The Washington Post)

In an election one side claims is “rigged” as the other was apparently targeted by Russian hackers and Wikileaks, voters in the Washington region may be concerned that some entity will alter the results on Nov. 8.

It’s possible, according to some local experts, although the likelihood of a significant attack on ballot boxes is exceedingly low.

“Everything is hackable,” said Jeremy Epstein, a senior computer scientist at SRI International, a nonprofit California-based think tank. “Everything could have bugs in it.”

On one hand, the U.S. election system is hard to sabotage. Anyone trying to swing the electoral college would have to meddle with voting machines in jurisdictions from Alaska to Maine — or at least about a dozen swing states.

“You’d have to be pretty good at microtargeting,” said Jamil N. Jaffer, director of the Homeland and National Security Law Program at George Mason University. “To have an impact, you would have to know where it’s going to be close.”

And different voting technology means different weaknesses. The District, Maryland and many counties in Virginia use paper ballots — a gold standard for election-watchers. These ballots are scanned and counted electronically, leaving behind a hard copy of each voter’s preferences.

“It seems old-school, but if you have good security practices and a good ballot chain of custody . . . it’s more indelible than bits and bytes in the ether,” said Pamela Smith, president of the nonpartisan Verified Voting, a nonprofit that works for fair elections.

Cameron Sasnett, the general registrar for Fairfax County, said the county’s election results are secured partly by pen and paper.

“That is the record of our election and, at the end of the day, every voter gets to cast their ballot using that system,” he said. “There is an absolute, 100 percent record of what the voter wanted.”

But others say machines, which are often used to count paper ballots, can malfunction. And even if computer voting results are backed up on paper, the backup is only worthwhile if results are audited — that is, if a statistically significant sample of ballots is double-checked to make sure machines have counted them correctly.

Such audits are performed by hand in the District, officials said. But in Maryland, the audit is performed by a separate computer system partly because election officials said human auditors can make mistakes.

“It’s just completely independent,” said Nikki Charlson, deputy state administrator of the Maryland Board of Elections. “You take a data file and you give it to someone else and you’re saying, ‘Count this.’ ”

Meanwhile, Virginia doesn’t perform audits, and some counties in the state don’t use paper in voting — policies that have drawn criticism. Although some touch-screen voting machines that used wireless Internet were deemed vulnerable to hacking by the state’s board of elections and jettisoned this year, other touch-screen models may remain in operation in the state until 2020.

Virginia’s Department of Elections commissioner, Edgardo Cortés, said voters shouldn’t be concerned about “sensational” claims about election hacking.

“None of the equipment in the state is connected to the Internet,” he said. That “removes cyberthreats from remote or foreign hackers tampering with the system. In order to tamper with the machines, they need physical access.”

What if someone plans to tamper with Internet voting, offered by the District (and more than 30 states) for military and overseas residents even after the embarrassing hack of a test system in 2012, or tamper with voter registration — changing names, addresses or party affiliations? Such concerns also follow a warning from cybersecurity experts that Maryland’s online absentee-ballot system is dangerously vulnerable to tampering and privacy invasions.

David Dill, a professor of computer science at Stanford University and the founder of Verified Voting, pointed to registration system hacks in Arizona and Illinois, saying such attacks were his biggest concern.

“If people are able to modify voter registration records, it could cause serious problems,” he said. “It could cause chaos when someone shows up to vote.”

The outcome some election experts fear most is the possibility that excessive worry about a hacked election will dissuade people from voting.

“One way to be sure your vote isn’t counted is not to show up,” Smith said. “We don’t want voters to be terrified of voting.”

Republican presidential nominee Donald Trump’s claims about a rigged election could make this one of the most closely watched in American history. The Department of Homeland Security has met with officials in D.C. and 36 states, including Virginia, to discuss election security, local officials said.

Charlson, of Maryland’s election board, said it had devoted part of its website to “rumor control.”

“There are hypothetical risks in any system,” she said. “But we live in the world where we have to implement these systems, so the hypothetical risks can really muddy the water.”