WikiLeaks has published thousands of documents which it claims come from the CIA's Centre for Cyber Intelligence.
The release appears to grant an eye-opening look at the intimate details of the US agency's cyber espionage effort.
The dump could not immediately be authenticated, and the CIA did not return repeated messages seeking comment.
WikiLeaks has a long track record of releasing top secret government documents.
One expert who examined the dump, Rendition Infosec founder Jake Williams, told reporters it appears legitimate.
The dump could represent yet another catastrophic breach for the US intelligence community at the hands of WikiLeaks and its allies, which have repeatedly humbled Washington with the mass release of classified material.
Mr Williams added: "There's no question that there's a fire drill going on right now.
"It wouldn't surprise me that there are people changing careers - and ending careers - as we speak."
WikiLeaks, which had been dropping cryptic hints about the release for a month, said in a lengthy statement that the CIA had "recently" lost control of a massive arsenal of CIA hacking tools as well as associated documentation.
The radical transparency organisation said "the archive appears to have been circulated among former US government hackers and contractors in an unauthorised manner" and that one of them "provided WikiLeaks with portions of the archive".
Jonathan Liu, a spokesman for the CIA, said: "We do not comment on the authenticity or content of purported intelligence documents."
Mr Williams, who has experience dealing with government hackers, said that the voluminous files' extensive references to operation security meant they were almost certainly government-backed.
"I can't fathom anyone fabricated that amount of operational security concern," he said. "It rings true to me.
"The only people who are having that conversation are people who are engaging in nation-state-level hacking."
The documents cover a range of topics, including what appears to be a discussion about how to compromise smart televisions and turn them into improvised surveillance devices.
WikiLeaks said the leaked data also included details on the agency's efforts to subvert American software products and smartphones, including Apple's iPhone, Google's Android and Microsoft's Windows.
A "substantial library" of digital espionage techniques borrowed from Russia and other countries is in the data as well, WikiLeaks said.
Bob Ayers, a retired US intelligence official currently working as a security analyst, said the release was "real bad" for the agency.
Mr Ayers noted WikiLeaks has promised to release more CIA documents, saying this publication is just "the first full part of the series".
He added: "The damage right now is relatively high-level.
"(But) the potential for really detailed damage will come in the following releases."