Though the Office of Personnel Management has now disclosed the vast extent of data stolen on Thursday, federal investigators still won't say who was behind the attack.

"We're not really prepared to comment on the attribution behind this event," the National Security Council's Michael Daniel said in a conference call. Andy Ozment, assistant cybersecurity secretary at the Homeland Security Department, did confirm, however, that the government knows that the same "actor" was behind the two huge attacks on OPM's files.

The first, revealed June 4, saw the personnel records of 4.2 million current and former government workers accessed. The second, made public about a week later, involved background investigatory records and ensnared a whopping 17.9 million new people — expanding to potential government workers, contractors and relatives of government employees.

Although National Intelligence Director James Clapper said that China was "the leading suspect" in public remarks last month, no other executive branch official has been willing to go there.

"I know that there are some who've speculated on who may be responsible at this point; I'm not willing to do that," White House spokesman Josh Earnest said earlier Thursday. "But I will note that there have been other incidents of inappropriate cyber activity that we have attributed to the Chinese."

"We have freely acknowledged that just about every time the president meets with his counterpart and when other U.S. officials meet with their Chinese counterparts, that the issue of China's conduct in cyberspace is one that we routinely raise," Earnest added.

Earnest has previously said, and Daniel underscored, that there are other, private ways to communicate with the perpetrators. And just because the administration didn't finger China publicly on Thursday doesn't mean that behind the scenes the U.S. can't or won't "take steps" to reprimand the hackers, Daniel said.

Earnest and other administration officials repeatedly mentioned the new "tools" the administration has access to counter and punish cybercrimes when asked how the U.S. will deal with the OPM hackers.

In the spring, Obama signed an executive order giving the Treasury secretary authority to "impose financial sanctions against individuals or entities that are engaged in cyber hacking or benefit from cyber hacking," Earnest said. "And that certainly puts more tools in the president's toolbox as he considers what steps can be taken to respond to either this incident or others that may emerge."

Republicans have critiqued President Obama's approach and handling of the OPM data breaches.

Senate Armed Services Committee Chairman John McCain, R-Ariz., in calling on Obama to replace OPM Director Katherine Archuleta, said that the administration needs to take a tougher line.

"I am troubled by the administration's lack of response and question how it continues to sit idly by as our adversaries exploit the United States on a continuous basis with little, or meaningless, reprisal," he stated.