A new report from the Senate Intelligence Committee highlighted the Obama administration's failure to properly warn and work with Twitter and Facebook to battle Kremlin-backed trolls interfering in the 2016 election.

The Senate report also concluded that the FBI’s examination of foreign influence on social media in 2016 was done “mostly through contractors” rather than by the FBI itself.

The 85-page report released Tuesday said Russian operatives working through the Kremlin-directed, St. Petersburg-based Internet Research Agency masqueraded as Americans online and “used targeted advertisements, intentionally falsified news articles, self-generated content, and social media platform tools” to push disinformation to tens of millions of social media users in the United States to harm Hillary Clinton, help Donald Trump, and sow discord.

The Senate report pointed out that, in its effort to understand Russian interference on Twitter, the FBI handed off its data-gathering and analysis responsibilities to a third party contractor, which the report said suggested the bureau either lacked resources or viewed the work "as not warranting more institutionalized consideration" and never contacted Twitter about possible Russian disinformation operations on its platform until after the election had ended.

Twitter’s general counsel told the Senate Intelligence Committee that “Twitter received no information from the U.S. government in advance of the 2016 election about state-sponsored information operations.”

A sample pro-Russian network analyzed by the FBI contractor in October 2016 had 13 Twitter accounts with more than 1.5 million followers, and four of the accounts had a “reciprocal relationship” with Russian Ministry of Foreign Affairs social media employee Sergey Nalobin, whose visa extension had been denied by the United Kingdom a year earlier for his connection to a U.K. political group named Conservative Friends of Russia.

The FBI contractor said more than 70% of the network’s tweets included links to websites outside U.S. media that were supportive of the Trump campaign, along with websites with content from Russian disinformation sites or with more covert connections to the Kremlin. The Russian accounts specifically promoted U.S. election-related news and leaked Democratic Party emails published by WikiLeaks as well as spread allegations of voter fraud.

After pressure from the Senate Intelligence Committee after the 2016 election, and following an internal investigation, Twitter told the Senate in late 2017 that the Internet Research Agency produced 10.4 million tweets across 3,841 Twitter accounts.

Facebook told the Senate that it reported interference from Russian actors to law enforcement officials in 2016 who “subsequently shared useful feedback.” But the Senate said the FBI failed to proactively communicate with the social network.

Facebook handed over information to the Senate that revealed that the Internet Research Agency created 81 Facebook Pages, including roughly 61,500 posts and 3,393 advertisements, and there were close to 116,000 Instagram posts across 133 Instagram accounts. Google told the Senate the Internet Research Agency created approximately 1,100 YouTube videos, totaling just 43 hours of video, across 17 channels.

The report concluded that federal efforts to find and fight foreign influence efforts on social media have improved since the last presidential election. Twitter told the Senate the company has relationships with relevant law enforcement groups such as the FBI Foreign Influence Task Force and Homeland Security’s Election Security Task Force, and Facebook told the committee that the company now coordinates with the FBI’s Counterintelligence Division and the DOJ’s National Security Division as well as works with Homeland Security, the FBI, and state secretaries of state detecting and stopping information operations.

The report is the second volume of the Senate Intelligence Committee’s yearslong efforts to uncover the full extent of Russian interference in the 2016 presidential election. Its first volume, released in July, concluded Russian operatives had tried to invade election systems in all 50 states, although there was no evidence that any votes were changed.

This deep dive into Russia’s efforts on social media by the Senate was in parallel to the conclusions reached by special counsel Robert Mueller and the intelligence community that Russian military intelligence was responsible for the hacking of the Democratic National Committee’s emails and for handing those stolen records to WikiLeaks for dissemination.