At the Cheltenham Literature Festival, Clinton said Russia launched an information war during the presidential campaign.
"It is a clear and present danger to western democracy and it is right out of Putin's playbook," she said.
Clinton also said the US was "in the dark about the weaponisation of social media." In recent weeks, Facebook, Twitter and Google have come under intense scrutiny over their platforms' being inadvertently used in Russia's campaign to spread misinformation during the election.
"We know Russian agents used Facebook, YouTube, Twitter and even Pinterest to place targeted attack ads and negative stories intended not to hurt just me but to fan the flames of division in our society," Clinton said. "Russians posed as Americans pretending to be LGBT and gun rights activists, even Muslims, saying things they knew would cause distress."
"In addition to hacking our elections, they are hacking our discourse and our unity. We are in the middle of a global struggle between liberal democracy and a rising tide of liberalism and authoritarianism."
She also warned that a "new kind of Cold War" is just getting started.
"Russia's weapons of choice may not be tanks or missiles, but let me be clear: this is a new kind of Cold War and it is just getting started," she said, the Times reported. "We may in the 19th century have fought wars on land and sea and in the 20th century moved to the air, but in the 21st wars will be increasingly fought in cyberspace. America, the UK and its allies need to approach the threat with new courage and resolve together."
Assange took to Twitter to hit back at Clinton's latest remarks saying "there is something wrong with Hillary Clinton."
"It is not just her constant lying," he tweeted. "It is not just that she throws off menacing glares and seethes thwarted entitlement... "Something much darker rides along with it. A cold creepiness rarely seen."
There's something wrong with Hillary Clinton. It is not just her constant lying. It is not just that she throws off menacing glares and seethes thwarted entitlement. Watch closely. Something much darker rides along with it. A cold creepiness rarely seen.https://t.co/JNw2dkXgdu— Julian Assange ð¹ (@JulianAssange)October 15, 2017