The U.S. military’s top cyber warrior says it’s merely an “assumption” that the Chinese government was behind the recent hack at the Office of Personnel Management, or OPM — and not necessarily one he shares. That puts Adm. Michael Rogers, commander of U.S. Cyber Command and director of the National Security Agency, in opposition to unnamed sources within the U.S. government who blamed Beijing in June 4 interviews with the New York Times and Washington Post.

Rogers spoke in response to a question about how the National Security Agency was going about attributing the breach to the Chinese government. “You’ve put an assumption in your question,” he said. “I’m not going to get into the specifics of attribution. It’s a process that’s ongoing.”

The OPM hack may have exposed as many as 18 million records of government employees and job applicants, including people who applied for—and received—top-secret clearances.

Rogers’s hedged response, given during a question-and-answer session at the GEOINT symposium in downtown Washington, comes in stark contrast to the NSA’s approach to attribution during the Sony hack. In that case the FBI, working with the NSA and DHS, quickly named North Korea as the perpetrator, resulting in the prompt issuance of sanctions.

Rogers called that a great example of cross-agency collaboration. “Working across the United States government, DHS, FBI and the National Security agency, we were able to relatively quickly come to consensus about the characterization of the activity we were seeing coming in, which formed the basis of our attribution, and with a relatively high confidence factor, which allowed us to respond in a very public and direct way.”

Why hasn’t that collaboration worked in the case of the OPM hack? Said Rogers: “every dataset is different.”

OPM: Political and Technical Attribution

If you’re a conservative politician or a presidential candidate, there’s a good chance that you believe that the Chinese government is behind the OPM hack and that the Obama administration is being too easy on Beijing. Sen. Susan Collins, R-Maine, who serves on the Senate Intelligence Committee, told the Associated Press on June 5 that Beijing backed the intrusion. She called it “yet another indication of a foreign power probing successfully and focusing on what appears to be data that would identify people with security clearances.”

More recently, former Arkansas governor and 2016 GOP presidential hopeful Mike Huckabee wrote on his blog, “We should hack the cell phones of some prominent Communist party leaders, hack the bank accounts of intelligence officials, publicly humiliate Chinese families for political corruption, or wipe-out a few critical Chinese computer systems.”

The Obama administration has been more reluctant to publicly blame the Chinese government. “I can’t promise you that we’ll be in a position at any point in the future to make a grand pronouncement about who may have been responsible for this particular intrusion,” White House press secretary Josh Earnest said at a June 9 briefing.

The cybersecurity group FireEye says it’s “highly confident” that Chinese hackers did it, based on the kind of cables and telecommunications equipment involved, the type of data stolen, and the specific backdoors that the thieves used. “These backdoors, they’re commonly used by Chinese threat actors,” Michael Oppenheim, the intelligence operations manager at FireEye, told Defense One.

Oppenheim stopped short of formally accusing the Chinese government but added, “We believe that this aligns with Chinese interests.”

Oppenheim said that he was sympathetic to Rogers’s reluctance to formally attribute the breach to the Chinese government. “For someone in his position, you want to be 100-percent sure,” he said.

Meanwhile, we asked Rogers: what is he doing to shore up defenses or retaliate for the hack? “Now tell me,” he said, “you really think that as the director of the NSA and U.S. Cyber Command, I’m going to talk to you about that?”