WikiLeaks has published what it says are thousands of documents taken from the CIA's Center for Cyber Intelligence that are purportedly part of a U.S. cyberespionage toolkit.
The authenticity of the documents could not immediately be confirmed, and the CIA declined to comment.
But experts who have begun to examine the material say it appears legitimate.
If the release does prove to be authentic, it would be another catastrophic breach for the U.S. intelligence community at the hands of WikiLeaks and its collaborators.
WikiLeaks has been hinting at the release for the past month.
It said on March 7 that the CIA had "recently" lost control of a massive arsenal of CIA hacking tools and related documentation.
WikiLeaks said that "the archive appears to have been circulated among former U.S. government hackers and contractors in an unauthorized manner" and that one of them "provided WikiLeaks with portions of the archive."
CIA spokesman Jonathan Liu said the intelligence agency did "not comment on the authenticity or content of purported intelligence documents."