In a joint report issued on Thursday, the FBI and the Department of Homeland Security (DHS) provided technical details about the tools and cyber infrastructure they said Russian civilian and military intelligence services used for the hack attack, code named Grizzly Steppe.
The document said the cyber attack was carried out to “compromise and exploit networks and endpoints associated with the US election, as well as a range of US government, political, and private sector entities.”
However, it did not mention by name the Democratic National Committee (DNC) and Hillary Clinton’s campaign chairman John Podesta, whose emails were hacked and released during the campaign.
Federal investigators believe the initial cyber attack began in the summer of 2015 when a hacking unit, dubbed APT29, sent emails with hidden malware to more than 1,000 people working for the US government and political organizations.
Once someone clicked on the link, the hackers were able to infiltrate the system.
The simple trick developed into a far-reaching operation to interfere with the US presidential election, which saw billionaire businessman Republican Donald Trump defeat the heavily-favored Democratic nominee, Hillary Clinton.
In the spring of 2016, another hacking unit called APT28 targeted Democratic Party officials by sending malicious emails that “tricked recipients into changing their passwords.”
US intelligence officials believe that cyber attack gave Russian hackers access to the information of senior Democratic Party officials, which was “leaked to the press and publicly disclosed.”
“This activity by Russian intelligence services is part of a decade-long campaign of cyber-enabled operations directed at the US government and its citizens,” according to a joint statement from the FBI, DHS and the Office of the Director of National Intelligence.
“The US government seeks to arm network defenders with the tools they need to identify, detect and disrupt Russian malicious cyber activity that is targeting our country’s and our allies’ networks,” the statement added.
Investigators allege that Russian hackers have stolen information from and disrupted US government organizations, political organizations, think tanks, critical infrastructure and universities.
The analysis was released shortly after President Barack Obama issued a slate of retaliatory measures against Russia in response to the hacks, including the expulsion of 35 Russian diplomats.
Washington first publicly accused Moscow of a campaign of cyber operations against American political organizations in October but did not attribute motives at the time.
The intelligence community said earlier it believed the hacks were aimed at helping Trump win the election.
The president-elect has denied that Russia was involved in the cyber interference, and the Obama administration has been under pressure to provide evidence.
Moscow has rejected the US accusations as “unfounded,” and vowed to retaliate.