While the intelligence community's conclusion would likely be based on a range of intelligence data and sources, Trump seized on an admission Thursday by the Federal Bureau of Investigation that the Democratic National Committee rebuffed requests by federal agents to inspect computer servers that had been breached last year, forcing them to rely on third-party cyber security data to investigate the hack, the FBI said.
"The FBI repeatedly stressed to DNC officials the necessity of obtaining direct access to servers and data, only to be rebuffed until well after the initial compromise had been mitigated," the agency said. "This left the FBI no choice but to rely upon a third party for information. These actions caused significant delays and inhibited the FBI from addressing the intrusion earlier."
Trump argued that the admission supported his skepticism of the intelligence community's conclusions.
"So how and why are they so sure about hacking if they never even requested an examination of the computer servers?," Trump said on Twitter late Thursday evening. "What is going on?" In an interview Friday with the New York Times, Trump called the focus on Russian hacking "a political witch hunt."
While intelligence agencies hadn't previously confirmed that the DNC refused to provide access to its computers, they had disclosed that they depended on private cyber security companies.
In October, Timothy Barrett, spokesman for the Office of the Director of National Intelligence, said that US intelligence "independently observed technical activity that is consistent with the forensic evidence identified by a private cyber-firm and is consistent with our general understanding of cyber activities by the Russian government."
Although Barrett didn't name the company, CrowdStrike Inc. released technical details last year to demonstrate hacking attacks against the DNC and other groups were carried out by the Russian government.
CrowdStrike said it found evidence that hacking attacks were carried out by two Russian government hacking groups. One that it calls Fancy Bear is believed to be an arm of Russia's military intelligence agency. The other, which it calls Cozy Bear, is believed to be run by Russia's Federal Security Service, the successor to Russia's KGB, where Putin once worked.
Officials at the DNC disputed the latest FBI statement.
"Beginning at the time the intrusion was discovered by the DNC, the DNC cooperated fully with the FBI and its investigation, providing access to all of the information uncovered by CrowdStrike - without any limits," DNC Press Secretary Eric Walker said in a Thursday statement. "The DNC had several meetings with representatives of the FBI's Cyber Division and its Washington (DC) Field Office, the Department of Justice's National Security Division, and U.S. Attorney's Offices, and it responded to a variety of requests for cooperation, but the FBI never requested access to the DNC's computer servers."
President Barack Obama last week imposed sanctions against top Russian intelligence officials and agencies and expelled 35 Russian operatives from the US Russia has denied any role in the computer attack. Putin has vowed " a proportional" response, though is holding off until after Trump takes office January 20.
Trump praised Putin's restraint, calling him "very smart."
The public tug-of-war between Trump and the intelligence community he'll oversee starting January 20 has left many current and former analysts concerned about the potential fallout it could have.
"There is a difference between skepticism and disparagement," Clapper told senators Thursday when asked about Trump's repeated questioning of the intelligence agencies' conclusions and reliability. "Public trust and confidence in the intelligence community is crucial."
Obama echoed that thought. In a television interview Thursday he said that "it's going to be important to make sure the president and the intelligence communities are both working on the best possible information."
"My hope is that when the president-elect receives his own briefings and is able to examine the intelligence as his team has put together and they see how professional and effective these agencies are, that some of those current tensions will be reduced," Obama told WMAQ-TV in Chicago.