As tensions rise between the United States and Russia over the extradition of Edward Snowden, who leaked detailed information on the U.S. government’s surveillance programs, it is clear that the leaks have taken a political toll on the Obama administration. On Wednesday, the White House announced the cancelation of an upcoming bilateral meeting between Obama and Russian president Vladimir Putin before the G20 summit next month in St. Petersburg, Russia. A statement called Moscow's decision to grant asylum to the leaker, who is accused of espionage by the U.S. government, "disappointing".   

But the question remains whether Snowden’s leaks have actually damaged national security.

One side argues the leaks have done irreparable harm. The other says the leaks have not hurt national security. The precise, case-by-case impact of the leaks is unknown and likely will be for some time. More broadly, however, experts can identify ways in which the leaks could hamper counterterrorism efforts.

One way the leaks could harm counterterrorism efforts is that terrorists, alerted to the ways their communications can be monitored or gathered, can now devise ways to avoid detection. Not long after the Guardian and Washington Post first reported on Snowden’s leaks in June, reports came out that terrorists were changing their communications practices. "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. 

“That is one huge, huge blow to national security because you’re telling potential targets that, here’s a way that we’re collecting,” said Anthony Clark Arend, who heads the foreign service graduate program at Georgetown University.

But there’s a potential upside as well. “If the trade-off is that we now made it much, much harder for these networks to communicate, that actually could under certain circumstances help national security,” said Allan Friedman, a cybersecurity expert at the Brookings Institution. If the leaks create a situation where terrorists “have to rely on more couriers, more people that we can turn, more sources that are vulnerable to human intelligence and things like that, then you can imagine a benefit for national security.”

A second cause for concern comes from the fact of the leak itself, rather than the information that got out. Foreign intelligence often relies on informants or sources risking their lives to give U.S. intelligence officers sensitive information that, if released, could cost them their lives. In this sense, Arend fears that Snowden’s leaks could have a “chilling effect” on intelligence gathering.

An informant may trust the CIA case officer they interact with, Arend says, but they can’t be sure the “Snowdens of the world” won’t leak the information. “The long-term consequence is, potentially new sources will dry up.”

If the government responded to Snowden’s leaks by announcing they were restricting access to sensitive information, “sources might be more willing” to work with the U.S.

On the other side of the debate, defenders of the leaks argue that the information will not affect national security. The answer hinges on whether the leaked programs were considered critical to national security. In the case of the PRISM program which collects foreign electronic correspondence, there seems to be wide acceptance that the program has played an important role in counterterrorism efforts. But there is no consensus on whether the National Security Agency’s collection of all domestic phone records has actually proved necessary to national security. Sen. Patrick Leahy, D-Vt., who chairs the Senate Judiciary Committee, recently told intelligence officials that he is “not convinced” the program is effective.

Defenders of the leaks have also noted that Snowden’s disclosures were broad and not about the details of a specific operation. And they say that a leak by government official that the intelligence resulting in 22 embassy closures last week was gathered by listening in on an conference call of al Qaeda leaders, raises questions about the gravity of Snowden’s leaks. “If operational security was important,” said Friedman, “then why do we now know about the very specific instance” in this case? 

That’s a question the Snowden’s defenders were quick to point out. J. Kirk Wiebe, a former NSA intelligence analyst and whistleblower advocate who tried to bring oversight to the NSA’s programs after the Sept. 11 attacks, called the administration’s leak “orders of magnitude worse than anything Snowden has revealed,” in an email to reporters on Tuesday.

“It revealed a very explicit detail of our signals intelligence capacity and that directly informs very senior people in al Qaeda and related organizations that we were able to breach their security,” Friedman said, cautioning that the official who leaked this information was privy to more information than he is. “From that narrow perspective, that’s a big deal.”