“From the Russian perspective, this is punching back,” said Christopher Porter, a former C.I.A. officer who now studies cyberattacks at the firm FireEye. “We may not think that’s fair or justified, but that’s the way they see it.”
Mr. Porter said Mr. Putin had made no secret of his view that the United States, by promoting democracy in countries like Ukraine and Georgia, had interfered in Russia’s backyard and was trying to undermine its power.
What is missing from the public report is what many Americans most eagerly anticipated: hard evidence to back up the agencies’ claims that the Russian government engineered the election attack. That is a significant omission: Mr. Trump has been expressing skepticism for months that Russia was to blame, variously wondering whether it might have been China, or a 400-pound guy, or a guy from New Jersey.
There is only a whisper of dissent in the report — the eavesdroppers of the N.S.A. believe with only “moderate confidence” that Russia aimed to help Mr. Trump, while their colleagues at the C.I.A. and the F.B.I. have “high confidence.”
While most of Congress and much of the public appears to accept the agencies’ findings, Mr. Trump’s prominent doubts, accompanied at times by scorn for the agencies’ competence, has rallied a diverse array of skeptics on the right and the left. Under the circumstances, many in Washington expected the agencies to make a strong public case to erase any uncertainty.
Instead, the message from the agencies essentially amounts to “trust us.” There is no discussion of the forensics used to recognize the handiwork of known hacking groups, no mention of intercepted communications between the Kremlin and the hackers, no hint of spies reporting from inside Moscow’s propaganda machinery.
At the top of every page of the report is a disclaimer that acknowledges what is missing: “This report is a declassified version of a highly classified assessment; its conclusions are identical to those in the highly classified assessment, but this version does not include the full supporting information on key elements of the influence campaign.”
It offers an obvious reason for leaving out the details, declaring that including “the precise bases for its assessments” would “reveal sensitive sources or methods and imperil the ability to collect critical foreign intelligence in the future.”
The absence of any proof is especially surprising in light of promises on Thursday from the director of national intelligence, James R. Clapper Jr., that he would “push the envelope” to try to make more information public. Josh Earnest, the White House press secretary, said that Mr. Obama had directed officials to “make as much of it public as they possibly can.”
That will not be enough for many, as the initial reaction showed. While some welcomed the scope of the report, many others were disappointed.
“This is big: CIA, NSA & FBI publish perhaps the most high-profile intelligence community assessment in US history,” Thomas Rid, a professor at King’s College London and an expert on cyberwarfare, wrote on Twitter.
But Susan Hennessey, a former intelligence agency lawyer who is now the managing editor of the online journal Lawfare, wrote: “The unclassified report is underwhelming at best. There is essentially no new information for those who have been paying attention.”
Though the unclassified report is 25 pages long, counting the covers and several blank pages, the core analysis runs just five pages. That is less than the seven-page “annex” devoted to RT America, the television network. It is a description of the broadcaster from an intelligence report written in 2012, years before the election-related hacking took place.
The agencies “have taken an all-source look at the broader Russian strategy,” said Mr. Porter, the former C.I.A. officer. The detailed description of RT’s tactics, though years old, he added, was included because they fit that strategy.
Mr. Trump may have been persuaded by his classified briefing on Friday on the Russian attack, which included everything that the unclassified report leaves out, even if the statement he issued afterward seemed lukewarm. But this report is unlikely to change the minds of skeptics who, like the president-elect, remember the intelligence agencies’ faulty assessments on Iraqi weapons of mass destruction and fear being misled again.