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.”