The response was tepid at best. After initially reviewing the thousands of files uploaded to the anti-secrecy group's website, several of the companies said that much of the data had been superseded by device updates.

Echoing Apple's claim that it was not panicked by the WikiLeaks disclosures, Google's director of information security and privacy Heather Adkins said: "As we've reviewed the documents, we're confident that security updates and protections in both Chrome and Android already shield users from many of these alleged vulnerabilities. Our analysis is ongoing and we will implement any further necessary protections."

Claiming that it had previously discovered and patched "many" of what it said were "the 14 iOS bugs" mentioned in the documents, Apple did say that it was working to "rapidly address" others.

According to the leaked documents, CIA hackers can access Apple iPhones, devices running Google's Android software and other devices, including internet-connected TVs, to capture text and voice messages before any encryption software puts the data beyond the agency's reach.

WikiLeaks says it has more CIA material to dump. In a press conference streamed live from the Ecuadorian Embassy in London, where he has been holed up since 2012, WikiLeaks founder Julian Assange said: "We have decided to work with [the manufacturers] to give them some exclusive access to the additional technical details that we have, so that fixes can be developed and pushed out, so that people can be secure."

His undertaking was met with a degree of scepticism.

"I'll believe that when I hear independent confirmation," said Jake Williams, founder of the threat intelligence firm Rendition Infosec. "This sounds like pure hype to me."

Dave Aitel, a former National Security Agency analyst who now runs the security firm Immunity, was also withering. "Is [Assange] also giving [the information] to security firms, so they can do forensic analysis? Having a hacker lecture us about vulnerabilities and disclosure is the height of rich hypocrisy."

CIA sources told reporters that the agency had become aware of a breach in its cyber security late last year, and that the likely suspect or suspects were contractors whose employers had been ordered to identify those who had access to the leaked material and to examine their computer logs and communications devices for clues that might identify the source of the leaks.

In the absence of evidence that it had attempted to use any of the leaked cyber weapons, Russian intelligence was given less credence as the likely perpetrator of the leak than any of the thousands of contractors retained by the CIA.

It would not be the first time that a contractor had pulled off such a heist. The high-profile leakers Edward Snowden and Harold Martin were contractors working for the National Security Agency, both employed by consulting firm Booz Allen Hamilton.

The timing of the WikiLeaks dump also raised questions about the group's partisanship - it was Moscow's preferred vehicle for the release last year of embarrassing Democratic Party emails on the eve of the Democratic Party's convention, the fruits of a hacking operation that the combined US intelligence agencies have concluded was intended as a leg-up for the Trump campaign.

This week's dump of documents was deeply embarrassing for the CIA, putting the agency on the back foot in the midst of what is seen as a vendetta by US President Donald Trump, who during the campaign declared "I love WikiLeaks", but who has noticeably failed to criticise the group in his new role as US commander-in-chief - despite resorting to Twitter to lash out at the intelligence agencies and others who have irked him.

Similarly, WikiLeaks has disclosed heaps of American classified information, but never any from Moscow. Michael Hayden, who headed the National Security Agency under George W. Bush and the CIA under Barack Obama, told CNN on Thursday: "[I believe] WikiLeaks is acting as an arm, as an agent, of the Russian Federation."

There was a bit of consternation too on Thursday, when a BuzzFeed reporter chanced on Nigel Farage, the former UK Independence Party leader and Trump ally who dined with the President in Florida less than two weeks ago, exiting the Ecuadorian embassy in London - and telling the reporter he couldn't remember what he had been doing in there.

After a muted initial response, the CIA let Assange have it on Thursday, claiming in a statement that by law it was required to confine its spying to foreigners and foreign countries.

Attacking Assange's credibility, it said: "As we've said previously, Julian Assange is not exactly a bastion of truth and integrity [and] despite the efforts of Assange and his ilk, CIA continues to aggressively collect foreign intelligence overseas to protect America from terrorists, hostile nation states and other adversaries."

Zeynep Tufekci, an associate professor at the School of Information and Library Science at the University of North Carolina, upbraided WikiLeaks for distorting the nature of the leaked files - which she said the group had represented as proof that the CIA had the capacity to do sweeping surveillance of many devices, as opposed to a single device at a time.

"WikiLeaks seems to have a playbook for its disinformation campaigns," she wrote in an op-ed in The New York Times.

"The first step is to dump many documents at once - rather than allowing journalists to scrutinise them and absorb their significance before publication. The second step is to sensationalise the material with misleading news releases and tweets. The third step is to sit back and watch as the news media unwittingly promotes the WikiLeaks agenda under the auspices of independent reporting."

Arguing that an initial burst of misinformation had spread by the time the media had sorted out the truth of the matter, she said: "On social media in particular, the spin and distortion continues unabated. This time around, for example, there are widespread claims on social media that these leaked documents show that it was the CIA that hacked the Democratic National Committee, and that it framed Russia for the hack.

"The documents in the cache reveal nothing of the sort."