Monaco told reporters that the results of the report would be shared with lawmakers and others.
“The president has directed the intelligence community to conduct a full review of what happened during the 2016 election process ... and to capture lessons learned from that and to report to a range of stakeholders, to include the Congress,” Monaco said during an event hosted by the Christian Science Monitor.
She said cyber-attacks were not new but might have crossed a “new threshold” this year.
When she was working as a senior Federal Bureau of Investigation (FBI) official in 2008, she said, the agency alerted the presidential campaigns of then-Senator Obama and Republican Senator John McCain that China had infiltrated their respective systems.
“We’ve seen in 2008 and in this last election system malicious cyber activity,” Monaco said.
In October, the US government formally accused Russia of a campaign of cyber-attacks against Democratic Party organisations ahead of the November 8 presidential election.
Confidential e-mails from the Democratic National Committee and John Podesta, a top adviser to Democratic nominee Hillary Clinton, were steadily leaked out via WikiLeaks in the months before the election, damaging Clinton’s ultimately losing White House effort.
The US Department of Homeland Security and the Office of the Director of National Intelligence in a statement on October 7, one month before the election, stated that “the Russian government directed the recent compromises of e-mails from US persons and institutions, including from US political organisations”.
“These thefts and disclosures are intended to interfere with the US election process,” they said.
Obama has said he warned Russian President Vladimir Putin about consequences for the attacks.
Asked if Republican President-elect Donald Trump’s transition team was not concerned enough about Russia’s influence on the election or about other threats to the United States such as infectious disease outbreaks, Monaco said it was too soon to say.
As a presidential candidate, Trump praised Putin and called on Russia to dig up missing e-mails from his opponent, Hillary Clinton, from her time as secretary of state under fellow Democrat Obama.
In an interview published on Wednesday with Time magazine for its “Person of the Year” award, Trump dismissed the findings of the country’s leading intelligence services.
Asked whether the intelligence was politicised, Trump answered: “I think so.”
“I don’t believe they interfered. That became a laughing point, not a talking point, a laughing point,” he added. “Any time I do something, they say ‘oh, Russia interfered’.”
“It could be Russia. And it could be China. And it could be some guy in his home in New Jersey.”