EDWARD SNOWDEN has demonstrated how easy it is to hack into an electronic voting machine still used in several states where voters go to the polls today.

He showed his 2.4 million Twitter followers a video in which experts were able to change the number of votes for each candidate in the computer memory - and also alter the paper-trail backup.

6 Security experts were easily able to hack into a Sequoia AVC Edge voting machine and change results

6 Cylance researchers used a modified flash memory card costing £24 to tamper with the machine Credit: YouTube / Cylance Inc.

He said hacking individual machines would be easy, but election officials would probably be able to detect fraud after polling day - which could be crucial if the result is contested.

Snowden said: "Researchers just demonstrated how to hack the official vote count with a $30 card.

"Little time to patch this vuln(erability), but can still forbid use of this model, run statistical analysis after polls close on rest to ID outliers."

He added: "Hacking voting machines: not that difficult. Hiding a secret deviation in votes from after-the-fact statistical analysis: nearly impossible."

Hacking voting machines: not that difficult. Hiding a secret deviation in votes from after-the-fact statistical analysis: nearly impossible. — Edward Snowden (@Snowden) November 7, 2016

The revelation comes as millions of Americans vote for their president today after the ugliest campaign in living memory - including claims by Donald Trump that the election is rigged.

In many US states voters record their choice by pressing a button or a computer touchscreen.

Now researchers at security firm Cylance have exploited a shocking vulnerability in one popular model of voting machine, the Sequoia AVC Edge Mk1.

It was widely used in 2008, and this year will still be used to tally votes in 13 states including swing battlegrounds Arizona, Pennsylvania and Wisconsin.

A video shows how the experts were able to hack into the machine using a PC memory card costing £24.

6 The cyber experts were able to change voting numbers, candidates details and the location of the polling district Credit: YouTube / Cylance Inc.

6 A printout appears to confirm the forged voting data in the test Credit: YouTube / Cylance Inc.

In a few steps they were able to make votes for one candidate count as votes for a rival.

They also easily changed names of candidates and other details.

Then they inserted a modified PCMCIA flash memory card into the machine and restarted it.

The altered and false data was retained in the system on relaunch and was also transferred to a printed paper version at the click of a button, making the results appear genuine.

Cylance said: “With access to the physical machine, we were able to produce a forged update with false voting data.”

The company's chief executive Stuart McClure said it was not only this model that was vulnerable but “anything that uses a touchscreen and compact flash model.”

Asked about the likelihood of such an attack on election day, he said: “We don’t have the threat intelligence to say it is going to happen, but we know it is quite easy and possible to do.”

6 The Sequoia AVC Edge voting machine was widely used in 2008 and is still used in 13 US states

Another security firm, Symantec, has previously revealed similar vulnerabilities in the AccuVote machine, used in Alaska, Utah and Georgia and in precincts in more than 15 other states.

They reprogrammed a PCMCIA ﬂash storage card, the kind used to set up machines by election officials via a slot on the side.

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Security expert Brian Varner said he was able to reset the card to allow an individual to vote multiple times, and also managed to program the card itself to cast multiple votes.

He said: "Anyone who knows how to program a chip card and purchases a simple $15 Raspberry Pi-like device, could secretly reactivate their voter card while inside the privacy of a voting booth.

"There is a real issue in play here. The idea that every vote counts is at the heart of our democracy, so relying on outdated technology to count those votes can undermine confidence in the process that is central to our system of government."

6 In many US states, voters touch a screen to cast their ballot in presidential and local elections and to choose officials such as judges

Republican candidate Donald Trump has been claiming for months the election is "rigged" and warned supporters polling fraud could keep him out of the White House.

Trump has said threatened he will not accept the result unless he wins.

His supporters have vowed to patrol outside polling stations to "check" for fraud - leading to fears of voter intimidation in districts with poor and ethnic minority electorates.

Pollsters have said the race for the White House is on a knife edge with fears of recriminations and even street violence if results are close.

In 2000 the result of the presidential election was delayed for weeks amid legal battles over recounts in the swing state of Florida.

It was finally settled in George W Bush's favour, and he took the state by 537 votes - giving the majority to become president.

Follow our U.S. election live blog for all the latest news and results.

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