WASHINGTON • Russia's cyber attack on the United States electoral system before President Donald Trump's election was far more widespread than has been publicly revealed, including incursions into voter databases and software systems in almost twice as many states as previously reported.
In Illinois, investigators found evidence that cyber intruders tried to delete or alter voter data.
The hackers accessed software designed to be used by poll workers on Election Day and, in at least one state, accessed a campaign finance database. Details of the attacks, in the summer and autumn of last year, were provided by three people with direct knowledge of the US investigation into the matter.
In all, hackers hit systems in 39 states, one of them said.
The scope and sophistication so concerned Obama administration officials that they took an unprecedented step - complaining directly to Moscow via a modern-day "red phone".
Last October, two of the people said, the White House contacted the Kremlin on the back channel to offer detailed documents of what it said was Russia's role in election meddling and to warn that the attacks risked setting off a broader conflict.
The new details, buttressed by a classified National Security Agency document recently disclosed by The Intercept, show the scope of alleged hacking that federal investigators are scrutinising as they look into whether Trump campaign officials may have colluded in the efforts.
MOSCOW NOT DONE MEDDLING
They're coming after America
FORMER FBI DIRECTOR JAMES COMEY, at the Senate Intelligence Committee investigating Russian interference in the election.
The newest portrayal of potentially deep vulnerabilities in the US' patchwork of voting technologies comes less than a week after former Federal Bureau of Investigation director James Comey warned Congress Moscow is not done meddling.
"They're coming after America," Mr Comey told the Senate Intelligence Committee investigating Russian interference in the election. "They will be back." A FBI spokesman in Washington declined to comment on the agency's probe.
Russian officials have publicly denied any role in cyber attacks connected to the US elections, including a massive "spear phishing" effort that compromised Mrs Hillary Clinton's campaign and the Democratic National Committee, among hundreds of other groups.
Russian President Vladimir Putin said in recent comments to reporters that criminals inside the country could have been involved without having been sanctioned by the Russian government.
One of the mysteries about the 2016 presidential election is why Russian intelligence, after gaining access to state and local systems, did not try to disrupt the vote. One possibility is that the American warning was effective.
Another former senior US official, who asked for anonymity, said a more likely explanation is that several months of hacking failed to give the attackers the access they needed to master America's disparate voting systems spread across more than 7,000 local jurisdictions.
Such operations need not change votes to be effective. In fact, the Obama administration believed the Russians were possibly preparing to delete voter registration information or slow vote tallying in order to undermine confidence in the polls.
One former senior US official expressed concern that the Russians now have three years to build on their knowledge of US voting systems before the next presidential election, and that there is every reason to believe they will use what they have learned in future attacks.
As the first test of a communication system designed to de-escalate cyber conflict between the two countries, the cyber "red phone" - not a phone, in fact, but a secure messaging channel for sending urgent messages and documents - did not quite work as the White House had hoped. The White House provided evidence gathered on Russia's hacking efforts and reasons why the US considered it dangerously aggressive. Russia responded by asking for more information and providing assurances that it would look into the matter, even as the hacking continued.
Mr Eric Schultz, a spokesman for former president Barack Obama, said: "Last year, as we detected intrusions into websites managed by election officials around the country, the administration worked relentlessly to protect our election infrastructure."
Illinois, which was among the states that gave the FBI and the Department of Homeland Security almost full access to investigate its systems, provides a window into the hackers' successes and failures.
In early July last year, a contractor who works at the state board of elections detected unauthorised data leaving the network, said Mr Ken Menzel, general counsel for the Illinois board of elections.
The hackers had gained access to the state's voter database, which contained information such as names, dates of birth, gender, driver's licences and partial Social Security numbers on 15 million people. As many as 90,000 records were ultimately compromised.