An attempt to illegally obtain absentee ballots in Florida last year is the first known case in the U.S. of a cyberattack against an online election system, according to computer scientists and lawyers working to safeguard voting security.

The case involved more than 2,500 “phantom requests” for absentee ballots, apparently sent to the Miami-Dade County elections website using a computer program, according to a grand jury report on problems in the Aug. 14 primary election. It is not clear whether the bogus requests were an attempt to influence a specific race, test the system or simply interfere with the voting. Because of the enormous number of requests – and the fact that most were sent from a small number of computer IP addresses in Ireland, England, India and other overseas locations – software used by the county flagged them and elections workers rejected them.

Computer experts say the case exposes the danger of putting states’ voting systems online – whether that’s allowing voters to register or actually vote.

“It’s the first documented attack I know of on an online U.S. election-related system that’s not (involving) a mock election,” said David Jefferson, a computer scientist at Lawrence Livermore National Laboratory who is on the board of directors of the Verified Voting Foundation and the California Voter Foundation.

Other experts contacted by NBC News agreed that the attempt to obtain the ballots is the first known case of a cyberattack on voting, though they noted that there are so many local elections systems in use that it's possible that a similar attempt has gone unnoticed.

There have been allegations of election system hacking before in the U.S., but investigations of irregularities have found only software glitches, voting machine failures, voter error or inconclusive evidence. Where there has been evidence of a computer security breach -- such as a 2006 incident in Sarasota, Fla., in which  a computer worm that had been around for years raised havoc with the county elections voter database -- it was unclear whether the worm's appearance was timed to interfere with the election.

In any case, experts say they’ve been warning about this sort of attack for years.

Tim Chapman / Miami Herald

About 2,000 rejected absentee ballots at Miami-Dade Elections Department, mostly for lack of signatures or review of signatures from the last election.

“This has been in the cards, it’s been foreseeable,” said law Professor Candice Hoke, founding director of the Center for Election Integrity at Cleveland State University.

The primary election in Miami-Dade County in August 2012 involved state and local races along with U.S. Senate and congressional contests (see a sample ballot here). The Miami Herald, which first reported the irregularities, said the fraudulent requests for ballots targeted Democratic voters in the 26th Congressional District and Republicans in Florida House districts 103 and 112. None of the races’ outcomes could have been altered by that number of phantom ballots, the Herald said.

Overseas “anonymizers” -- proxy servers that make Internet activity untraceable -- kept the originating computers’ location secret and prevented law enforcement from figuring out who was responsible, according to the grand jury report, issued in December. The state attorney’s office closed the case in January without being able to identify a suspect.

Read the Miami-Dade County grand jury report (PDF)

Then came the Herald report, which said that three IP addresses in the United States had been identified among those sending the requests and that there had been a delay in getting that information to investigators, which a Miami-Dade elections official confirmed to NBC News. Terry Chavez, spokeswoman for the state attorney’s office for Miami-Dade County, also confirmed to NBC News that the investigation was reopened to look into those IP addresses. Chavez said she could release no details on the investigation.

Rep. Joe Garcia won the Democratic primary in the 26th District and went on to win the general election. Jeff Garcia, his chief of staff and no relation, said last week that no state or federal investigators had contacted the congressman's office about the case.

State Rep. Jose Javier Rodriguez, a Democrat who won the District 112 seat, said Thursday that his office had not heard from investigators about the case either. A message left at the legislative office of state Rep. Manny Diaz Jr., the Republican who won the primary and the general election in District 103, was not immediately returned.

The Herald report said that as the requests began coming in, elections officials figured out that they were improper and started blocking the IP addresses. “I guess they finally gave up,” the newspaper quoted Bob Vinock, an assistant deputy elections supervisor for information systems, as saying. 

People who study election security say the fact that this attempt did not succeed should be of little comfort to election officials. They warn that attempts to attack voting systems are likely to increase.

“In this case the attack was not as sophisticated as it could have been, and it was easy for elections officials to spot and turn back,” said J. Alex Halderman, an assistant professor of computer science and engineering at the University of Michigan who studies the security of electronic voting. “An attack somewhat more sophisticated than the one in Florida, completely within the norm for computer fraud these days, would likely be able to circumvent the checks.”

Fraudulently obtaining absentee ballots is just one way elections might be subverted by digital means, experts say. Among the other methods and attack points:

•  Malware. Rogue software infects millions of home computers across the country. Jefferson said hackers could use malware to change votes or prevent them from being cast in an online election.
• Denial of service attacks. Jefferson said that hackers could use botnets to prevent election-system servers from working for hours, or perhaps longer. In fact, during an election in June 2012, a DOS attack hit the San Diego County Registrar of Voters' website, preventing voters from tracking the results.
• “Spoofing” of election websites. For example, Hoke said, legitimate requests for absentee ballots could be misdirected to another site. The data then could be misused, or the requests could hit a dead end, and voters would be left wondering where their ballots were.
• Exploiting software flaws in digital voting machines, known as DREs. The flaws could allow insertion of viruses or alteration of programming code that would change votes or delete them. (Read one description of hacking a voting machine.)
• Tampering with email return of marked ballots. Experts say email return is troublesome because of the multiple points for attack along the ballots’ electronic path. “The overwhelming consensus of the computer science community is don’t do it, it’s a bad idea,” said Jeremy Epstein, a senior computer scientist at SRI International. But in about half the states, email absentee ballot return is an option for members of the military and their families, along with some other U.S. citizens living overseas.
• Wholesale hijacking of an online voting system. In 2010, the District of Columbia Board of Elections and Ethics tested an Internet-based voting system for a week, asking computer experts to probe it for flaws. It took only 48 hours for a team led by Halderman to break in and take control of the site – even altering it so that the University of Michigan fight song played after a vote was cast.

Read the University of Michigan researchers’ report on the DC hack (PDF)

In terms of illegally getting access to absentee ballots, Epstein said, the attacker or attackers who failed in Florida might have had an easier time with Washington state and Maryland.

He said that last summer he demonstrated to the FBI a method of changing individual voters’ addresses and other information online in those two states by predicting their driver’s license numbers.

J Pat Carter / AP file

Absentee ballots for the general election marked for delivery to the U.S. Postal Service for mailing are seen at the Miami-Dade County election center in Doral, Fla., on Oct. 5.

First he used publicly available information to gain a voter’s full name and address. Then, he predicted the individual’s driver’s license number – which is based on a combination of the person’s name and numbers and letters -- and used the information to access their voter registration online. From there, he said, he could have changed their addresses and had absentee ballots sent out.

“Imagine if (attackers) changed the address for 2,500 votes. It could be completely automated, and they have the ballots sent to a post office box or whatever,” Epstein said. “Then the registered voters would have no idea until they tried to vote.”

In October, Halderman and other researchers sent letters warning elections officials in both states of the danger of staking system security on driver’s license numbers.

The letter to Washington officials (read it here in PDF) also said that other security features in the state’s MyVote system would be only a speed bump to a dedicated hacker.

“Although the MyVote system uses a CAPTCHA, an image of distorted text intended to deter simple automated attacks, this provides only minimal defense,” the letter says. “Attackers can use commercial services to defeat the CAPTCHA at a cost of less than $0.001 per voter.”

Shane Hamlin, assistant director of elections in the Washington Secretary of State's Office, told NBC News that state election officials have acted on the recommendations in the October letter and will require additional information to register to vote or change registration online.

Maryland election officials did not immediately return a call from NBC News seeking comment, but the Washington Post reported last month that Ross K. Goldstein, deputy administrator of the Maryland State Board of Elections, acknowledged the security hole and said the online voter registration system was being updated to address the issue.

“I believe technology can solve problems, and there are steps that we definitely can, and plan to, take to mitigate the risks,” the newspaper quoted him as saying.

While elections officials are attracted to the savings that online voting and registration systems promise, the cost of guarding online registration and voting systems is large, Hoke said. And that might negate the financial advantage of online balloting touted by some elections officials and vendors who want to sell electronic voting products.

“It’s cheap, if you don’t care whether elections are stolen,” she said.

That possibility -- of an election being stolen through digital means -- haunts researchers. For Jefferson, it’s a matter of national security.

“The legitimacy of government depends on it being impossible for single parties to change the results of elections,” he said.

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Joe Skipper / REUTERS

Republican U.S. Rep. Allen West, seen here on Oct. 18 during a campaign stop in South Palm Beach, Fla., isn't reacy to concede to Democrat Patrick Murphy.

Tea Party-backed Republican Congressman Allen West said he was still not ready to concede defeat on Sunday, almost two weeks after the Nov. 6 election, when the clock ran out on a partial recount in South Florida.

Results showing West trailing Democratic challenger Patrick Murphy by 1,900 votes were now expected to be turned over to the state Division of Elections for official certification.

West was granted a recount of early ballots in St. Lucie county at the weekend, but officials were unable to complete the process before time ran out at midday on Sunday.

"Today at noon, it became clear Patrick Murphy will be officially certified as the next congressman from the 18th Congressional District," said Murphy's campaign manager Anthony Kusich. "It is beyond time to put this campaign behind us."

Under Florida law, in the event of an incomplete recount the original returns are automatically submitted for certification by the state.

"This is election is far from over," said West's campaign manager, Tim Edson, in a statement calling the results "highly suspect."

"We will continue to fight on behalf of all voters in District 18 to ensure a fair and accurate count of their votes," he added, without saying how the campaign planned to challenge the result.

West, 51, a former Army lieutenant colonel, is seeking his second term in the U.S. House of Representatives, where Republicans held onto their majority in the election.   

With the help of the conservative Tea Party movement, West amassed one of the largest campaign war chests among House Republicans. His supporters include Americans for Prosperity, the conservative political advocacy group funded by the billionaire Koch brothers.   

Murphy, 29, a political newcomer in his first congressional race, ran a surprisingly well-backed campaign focused on branding West as a divisive right-wing extremist.

President Barack Obama beat Mitt Romney in Florida, NBC news reported Saturday, ending a four-day count with a thin margin of the popular vote, though substantial enough to avoid an automatic recount.

As a result, Obama garners the state's 29 electoral votes, for a national total of 332 votes to Romney's 206.

Regardless of the outcome, Obama had already clinched re-election.

The Florida Secretary of State's Office said that with almost 100 percent of the vote counted, Obama led Romney 50 percent to 49.1 percent, a difference of about 74,000 votes. That was over the half-percent margin where a computer recount would have been automatically ordered unless Romney had waived it.

There is a Nov. 16 deadline for overseas and military ballots, but under Florida law, recounts are based on Saturday's results. Only a handful of overseas and military ballots are believed to remain outstanding.

It's normal for election supervisors in Florida and other states to spend days after any election counting absentee, provisional, military and overseas ballots. Usually, though, the election has already been called on election night or soon after because the winner's margin is beyond reach.

But on election night this year, it was difficult for officials —and the media — to call the presidential race here, in part because the margin was so close and the voting stretched into the evening.

If there had been a recount, it would not be as difficult as the lengthy one in 2000. The state no longer uses punch-card ballots, which became known for their hanging chads. All 67 counties now use optical scan ballots where voters mark their selections manually.

Republican George W. Bush won the 2000 contest after the Supreme Court declared him the winner over Democrat Al Gore by a scant 537 votes.

The win gave Obama victories in eight of the nine swing states, losing only North Carolina. In addition to Florida, he won Ohio, Iowa, New Hampshire, Wisconsin, Virginia, Colorado and Nevada.

The Associated Press contributed to this report.

DAYTONA BEACH, Fla. – Mitt Romney responded to President Barack Obama's latest attack, accusing the GOP nominee of forgetting and shifting his positions on issues on Friday night by calling out the Obama campaign for resorting to "petty attacks and silly word games" in the final three weeks of the campaign.

"Have you been watching the Obama campaign lately?" Romney asked a crowd of several thousand supporters at an outdoor event Friday night. "It's absolutely remarkable. They have absolutely no agenda for the future. No agenda for America. No agenda for a second term. It's a good thing they won't have a second term."

"They've been reduced to petty attacks and silly word games. Just watch it. The Obama campaign has become the incredible shrinking campaign," Romney said.

Romney's counter came after Obama unveiled a new line of attack at a rally earlier Friday in Virginia, coining the term "Romnesia" to describe satirically how Romney might have changed positions on issues by forgetting his past stances over the years.

“He's changing up so much -- backtracking and sidestepping. We've got to name this condition that he's going through. I think ... I think it's called 'Romnesia'. Now, I'm not a medical doctor but I do want to go over some of the symptoms with you. Because I want to make sure nobody else catches it,” the president said.

“If you say you're for equal pay for equal work, but you keep refusing to say whether or not you'd sign a bill that protects equal pay for equal work, you might have Romnesia,” Obama said to laughs. “If you say women should have access to contraceptive care, but you supported legislation that would let your employers deny you contraceptive care, you might have a case of Romnesia.”

Romney continued his own new assault on what he claimed was the lack of a second term agenda for the Democratic administration, a chord he has been striking at each appearance since the second debate.

"The president has no jobs agenda. We keep on asking him: What are you going to do to create jobs? He has nothing new. He says well we're going to go forward," Romney said. "Forewarned is a better term."

“Here’s just part of President Obama’s agenda for a second term: double our exports, create a million manufacturing jobs, cut oil imports in half, recruit 100,000 math and science teachers, train two million workers at community colleges, and reduce the deficit by more than $4 trillion," Obama campaign spokesman Danny Kanner responded in a statement.

Romney and vice presidential nominee Paul Ryan's joint appearance in the Sunshine State, their third such joint stop here -- and Romney's plan to stay here through Monday night's debate -- reflect the closeness of the race here. A new poll from CNN/ORC shows the Florida in a statistical dead heat -- with Romney claiming 49 percent of the vote to Obama's 48 percent.

At a fundraiser in Boca Raton on Friday, Ryan told donors their late gifts could make the difference in financing a turnout operation that will determine the winner of this often-decisive battleground state.

"Your dollars are going straight to voter turnout, to voter education, to cutting thru the clutter, to giving the country a choice that they themselves deserve," Ryan said.

MIAMI, Fla. – Former President Bill Clinton on Tuesday continued to relish his unofficial role as the chief explainer of what is at stake in the November election, this time tailoring his message to the young crowd gathered at Florida International University.

Speaking to 2,300 supporters, including many students, Clinton used the 11th anniversary of the Sept. 11 attacks as a chance to talk about the importance of service -- specifically voting.

"I keep reading that young people are not quite sure if they're going to vote. I tried to argue down in Charlotte last week that that's a mistake, that we have a lot of reasons to vote and we have a good candidate to vote for," said Clinton.

Young Americans were a key group that helped propel President Obama to victory in 2008, but polling shows that enthusiasm has not matched the level of four years ago.

In Florida, Clinton also reached out to older Americans, saying Republicans have spread "misinformation" about Democrats plans for Medicare.  It is the same misinformation that led the GOP to an electoral landslide in the 2010 midterms, Clinton said.

"They got away with running this old dog through the chute in 2010 and countless thousands of seniors voted because they were given misinformation against people who supported a plan to strengthen Medicare," said Clinton. "So I'm talking about it everywhere because the first time they did it, it was their fault. If we let it happen again, it is out fault."

Clinton also fought back against the claims vice presidential nominee Paul Ryan and other Republicans have made, arguing that Obama has cut $716 billion from Medicare.

"Embarrassingly for the Republicans, the nominee for vice president who's chair of the house budget committee, produced a budget that had exactly the same callings for savings that the Obama budget did, and that was true in 2010 when they were advertising against it. Now, as I said in Charlotte, you got to hand it to them; it takes real brass to attack people for doing what you did," Clinton said.

According to a Pew Research poll, Clinton's keynote address last week was for many the highlight of the Democratic convention, drawing an even more favorable rating than Obama's speech.  It was a straight-forward assessment of why the president deserves re-election, and it is the same message he took down to the swing-state of Florida on Tuesday. The man who has been dubbed the "Explainer-in-chief" heads to Orlando Wednesday for another rally.

Along with Medicare and the economic recovery, Clinton also defended the president's record on solar energy and the often shied away topic of the stimulus, saying it helped prevent even high levels of unemployment.  All of it, Clinton said, has laid the foundation for an economic recovery that will be at risk if Mitt Romney is elected.

"The test is not whether you think everything is hunky-dory. If that were the test, the president would vote against himself.  He said that everything is not hunky-dory," he said. "The test is whether he's taken us in the right direction, and the answer is yes."

OXFORD, OH -- Appearing at his alma mater Wednesday, Republican vice presidential nominee Paul Ryan weighed in on the Medicare debate for the first time before voters on the campaign trail.

“The president, I'm told, is talking about Medicare today,” Congressman Ryan told the couple-thousand-person crowd at Miami University. “We want this debate, we need this debate, and we will win this debate.”

The Medicare debate is quickly becoming a key issue going into the November election especially after Ryan was selected as Mitt Romney’s running mate. Ryan, the House Budget Committee chairman, authored a controversial bill that would transform the health care system for seniors and has been taking heat for it from President Obama and Democrats.

While Ryan touched on the topic on a college campus Wednesday, he mostly attacked Obama and failed to offer specifics of what a Romney-Ryan plan would look like.

The day after the presumptive GOP presidential nominee himself stumped in the Buckeye State, Paul made his first appearance in the state since being announced as VP and even recalled several local spots he would frequent when he was a student here.

“Ohio is so important. You know this. You’re used to it. The Buckeye state could very well determine the future of our country for a long time,” Paul told the crowd outside about the third battleground state he has been in.

Ohio Senator Rob Portman – once considered the frontrunner for the VP pick – was on hand for Ryan’s visit to his state and praised Romney’s selection of the seven term Wisconsin congressman.

“Paul Ryan, as I said earlier, is a Redhawk, so Redhawks should be soaring today, but he is also a very good friend,” Portman said. “He is one of those guys in Congress that is there for the right reasons and you know what that reason is? It is about his family. It’s about your family. It's about being sure that the American dream can be restored. That’s what Paul Ryan is about.”

The crowd was made well aware that Portman was nearly selected to join Romney’s ticket.

“I want to tell you, it was sort of funny because as you know [Portman] was seriously considered for this job,” Ohio Gov. John Kasich told the crowd before Portman’s remarks. Portman’s “wife told me … 17-year-old Sally is the vice president of her class and Rob’s wife said this family can only stand one vice president at a time.”

Congressman Ryan, meanwhile, had nothing but kind words to say about Portman.

“Rob is a very close friend, we've been through a lot together,” Ryan said. “I just want to tell you what a special man this is. I thank you for your service Rob Portman you are one great United States senator.”