Investigators find evidence attackers tried to modify voter data, reports Bloomberg.

Citing sources "with direct knowledge of the US investigation" into Russia's information operations campaign during the 2016 US presidential election campaign, Bloomberg News' Michael Riley and Jordan Robertson report that Russian hackers struck at far more states' election offices than previously known. A total of 39 states had election systems targeted by the Russians, Bloomberg's sources said—including Illinois, where attackers broke into voter rolls and tried to delete or modify voter registration data in an attempt to disrupt voting on Election Day.

The scope of the attacks was so broad, Bloomberg reports, that in October of 2016, then-President Barack Obama directly called Russian Federation President Vladimir Putin on the "cyber-hotline." The cyber-hotline "red phone" was set up in 2013 by Obama and Putin as part of an effort to reduce the risk of a "cyber incident" escalating; Obama used it to present evidence of the attacks and warn Putin that the intrusions could trigger a larger conflict between the US and Russia.

As the National Security Agency analysis recently leaked by contractor Reality Winner suggested, the attackers also gained access to software used by poll workers to check voter eligibility, according to Bloomberg's sources. In another unnamed state, attackers accessed a campaign-finance database.

The Bloomberg report comes days after former FBI Director James Comey told the Senate Select Committee on Intelligence that he had "no doubt" that state-directed Russian hackers had attempted to interfere with the 2016 election, stating, "They're coming after America... they will be back."

Russian officials have repeatedly denied that there was a government-backed effort to disrupt the US election. However, at a recent economic summit in St. Petersburg, Putin acknowledged that Russian hackers may have been involved in the election interference, though he claimed they would have been acting alone. "Hackers are free people, just like artists who wake up in the morning in a good mood and start painting," Putin said on June 1. "If they are patriotically minded, they start making their contributions—which are right, from their point of view—to the fight against those who say bad things about Russia."