CBS News has reported that the FBI and CIA have started an investigation to find the person who provided WikiLeaks with secret documents.

The investigation is linked to the WikiLeaks publication of almost 9,000 pages that detailed the CIA’S hacking operations. According to the documents, the CIA uses its own malware to hack into anyone’s electronics and spy on them. The agency even has malware from Russia, and other countries, which means agents can make an attack look like it came from that country.

CBS News reported:

Sources familiar with the investigation say it is looking for an insider — either a CIA employee or contractor — who had physical access to the material. The agency has not said publicly when the material was taken or how it was stolen.

Much of the material was classified and stored in a highly secure section of the intelligence agency, but sources say hundreds of people would have had access to the material. Investigators are going through those names.

The FBI and CIA warned about an investigation a day after Wikileaks published the documents. In response, Wikileaks state it received the documents from someone within the agency:

WikiLeaks said the CIA recently “lost control” of the majority of its hacking arsenal. “This extraordinary collection, which amounts to more than several hundred million lines of code, gives its possessor the entire hacking capacity of the CIA,” the site said in a statement. “The archive appears to have been circulating among former U.S. government hackers and contractors in an unauthorized manner, one of whom has provided WikiLeaks with portions of the archive.”

Last week, CIA Director Mike Pompeo lashed out against Wikileaks and Julian Assange:

“It is time to call out WikiLeaks for what it really is: A non-state hostile intelligence service often abetted by state actors like Russia,” he said.