By Barbara Starr
The U.S. intelligence community says terrorists are trying to change the way they communicate because of what they learned from Edward Snowden's admitted leaks of classified information about government surveillance programs.
"We can confirm we are seeing indications that several terrorist groups are in fact attempting to change their communications behaviors based specifically on what they are reading about our surveillance programs in the media," a U.S. intelligence official told CNN.
He emphasized these are terrorist groups operating outside the United States and are not limited to al Qaeda affiliates.
Intelligence has been gathered on both Sunni and Shia groups, he said, noting the risk to national security is that the groups "go dark" in terms of the U.S. ability to listen to them and watch them until it can "reacquire them" through new means.
As for whether that poses an immediate threat to national security, "I am not telling you people are dying, I am telling you terrorists are already trying to change their behavior," he said.
As the U.S. intelligence community tries to determine what damage Snowden may have caused national security, one assumption is underpinning the US analysis: The belief that China copied and read whatever documents he had in Hong Kong.
"That's a safe assumption. That's where people are starting on this," said one administration official with knowledge of the "damage assessment" review. "Given his stay in Hong Kong and the number of days he was there, the assumption has to be everything he had was compromised."
The official didn't dismiss the notion that Russia may have done the same thing.
But it's not clear what material from the leaks of classified information about National Security Agency telephone and e-mail surveillance programs Snowden may have taken from Hong Kong to Moscow, or what he may have been forced to leave behind.
U.S. and Russian intelligence services are communicating on the Snowden matter, but the official declined to offer any details.
The assessment on how much damage Snowden's leaks of information, including leaks to the Guardian and the Washington Post this month could last for months, the official said.
"We may not have a full handle yet on everything he has," he said.
Separately, a second, senior U.S. intelligence official agreed.
"We are trying to figure out the totality of what may have been compromised," that official said.
He said the United States is "highly concerned that sources and methods could have been compromised" by Snowden based on his public statement he could access the names of U.S. intelligence personnel.
"It could lead to potentially grave damage," he said.
The United States is continuing to assess what documents he could have accessed and what he downloaded.
Beyond that, officials need to determine how many computers Snowden may have traveled with, the size of hard drives, and how much material they could handle.
They also are still trying to determine if some material was handed off to news media without Snowden keeping copies with him in Hong Kong.
"The greatest concern now is the unknown," the administration official told CNN. "What else might he have had access to, is there another shoe to drop?"
The worry is that Snowden, who was a contract NSA computer systems administrator, may have been able to access a wide range of material beyond that of his immediate job responsibilities.
The administration official also said the U.S. intelligence community is concerned Snowden may have established some type of "doomsday insurance," threatening to publicize an online link to all his material that everyone could access if he is taken into custody.
For each step of the assessment, the United States also has to determine further what the disclosures may have on the ability of terrorists to change tactics.
The administration official offered an example of one concern: Terrorists may be less inclined to communicate via "clean" e-mail accounts that have no links to them because they believe the U.S. government can track those.
When Snowden first admitted he was responsible for leaking information about the surveillance programs, he denied his motive was to harm the United States or aid China or an enemy of the United States.
"Anyone in the positions of access with the technical capabilities that I had could suck out secrets, pass them on the open market to Russia; they always have an open door as we do. I had access to the full rosters of everyone working at the NSA, the entire intelligence community, and undercover assets all over the world. The locations of every station, we have what their missions are and so forth," he said.
"If I had just wanted to harm the U.S. You could shut down the surveillance system in an afternoon. But that's not my intention," he said.