The FBI is working to track down whoand shared them on social media, and at the same time, the Pentagon is reducing the number of people who have access to the kind of classified information that has been leaked.
The number of people on government-wide distribution lists who receive classified updates has been culled significantly since Friday, U.S. officials said. Before thewas revealed, about 1,000 people usually had access to these types of documents. CBS News has reviewed a number of the leaked documents, all of which are color printouts with text, graphics or maps that appear to have been folded, unfolded and then photographed and shared on social media sites including 4Chan and Discord.
The Pentagon's internal review of the matter will be led by Milancy Harris, deputy under secretary of defense for intelligence and security. The review will probe the scope and scale of the leak and the impact on the U.S. and allies' national security, and examine how information flows and who has access to it.
The FBI is leading the criminal investigation, which is only in its early stages, according to a U.S. official familiar with the probe. Former officials familiar with leak investigations predicted that identifying the source could happen quickly because "the universe of possibilities is relatively small."
One U.S. official indicated that not all printers are authorized to print classified documents, and those that have this authorization register a unique ID when printing, so this may provide some clues into the search for the leaker.
In the intelligence community, spokespeople for the Office of the Director of National Intelligence (ODNI), CIA, National Security Agency and National Reconnaissance Office largely declined to comment on the leaked documents, referring inquiries to the Department of Justice as it conducts an investigation into the source. It's not yet clear whether ODNI has launched or will launch its own risk assessment.
However, CIA Director William Burns, at an event hosted by Rice University's Baker Institute for Public Policy Tuesday evening, briefly referenced the classified documents leak in taking questions after a speech. He called the leak "deeply unfortunate" and a priority "certainly as intense as anything" in his inbox.
"It's something that the U.S. government takes extremely seriously," he added, and cited the FBI and Defense Department investigation as reason for him not to elaborate further.
One senior U.S. intelligence official offered a brief and bleak assessment of the leaks: "It's not good."
Nonetheless, a U.S. official noted Tuesday that he has seen no indication other than media reports that Ukraine has been forced to change its battle plan as a result of the leaked documents.
And several former intelligence officials, including two who served in senior capacities during theand , said this disclosure — what is known of it so far — is not entirely comparable in its scale.
"In a sense, what this tells you is that the systems that were put in place to prevent massive theft of information on, for example, thumb drives, is working," one former senior official said. "Here, it appears instead that someone actually took documents out of the building the old-fashioned way."
These officials, who were familiar only with press summaries of the documents and couldn't speak to their authenticity, acknowledged some of the disclosures appear particularly damaging for signals intelligence sources — electronic accesses that are difficult to create, or recreate once gone — but appear, for now, to have minimal effect for human sources.
"I don't think there's huge damage here," one official said, including for battlefield ramifications in Ukraine. "People are assuming this was all new to the Russians — it probably wasn't."
The documents are said to resemble daily briefing materials for the top members of the Joint Chiefs of Staff, who usually receive them six days a week. A staff of several dozen people put together a first cut of materials sourced from across government agencies, which can include the kind of graphics and analysis that have appeared in the leaks.
"U.S. agencies should be out there looking for classified information, doing sweeps of the web, every day," one official said. "This took way too long to identify."
David Martin contributed to this report.
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