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© Kevin Lamarque / Reuters
US President Barack Obama has admitted security chiefs have not yet identified those behind a sophisticated cyber-attack which crippled some of the world's biggest websites last Friday.

Two major distributed denial of service attacks (DDoS) on internet traffic management company Dyn brought down more than 80 popular sites, such as PayPal, Reddit, Amazon, Twitter and Spotify.

The data overload, thought to be powered by small items capable of connectivity - 'Internet of Things' devices - disabled sites for three hours and involved "10s of millions of IP addresses."

Dyn said in a statement that while they regularly experience DDoS blitzes, this large-scale attack was different and "more global in nature".

An update from Dyn reveals the attack began with a malware-infected botnet, which allowed millions of "discrete IP addresses" to be commandeered.

Speaking on 'Jimmy Kimmel Live' on Monday, Obama said that despite the FBI investigating the situation, the US "don't have any idea who did that."

He added that cyber security would be a big issue for his White House successors.

"One of the biggest challenges for the next president and the president after that and the president after that is going to be how do we continue to get all the benefits of being in cyberspace but protect our finances, protect our privacy."

"What is true is that we are all connected. We're all wired now," he said.

Obama's admission over the attack source comes as his administration continues to propagate a 'Red Scare' by insisting Russian state-backed hackers have been trying to intefere with the US election.

On October 7, the Department of Homeland Security said it was "confident" the Russian government had directed cyber-attacks, but offered no evidence to that effect.

"The recent disclosures of alleged hacked e-mails on sites like DCLeaks.com and WikiLeaks and by the Guccifer 2.0 online persona are consistent with the methods and motivations of Russian-directed efforts," a US government statement said.

"We believe, based on the scope and sensitivity of these efforts, that only Russia's senior-most officials could have authorized these activities."