The CIA’s decision to pull out its operatives was meant to safeguard agents whose affiliation to the agency might have been discovered.
The Central Intelligence Agency declined to comment.
About 21.5 million former, current and prospective federal employees and contractors were affected by the OPM data breach in the spring.
By comparing the stolen OPM records with the names of those working at the USA embassy in Beijing, parties could effectively identify who is a spy, since intelligence agents are not subject to State Department background checks.
USA officials suspect the data was stolen in an attempt to identify US spies, who could then be recruited or coerced into providing sensitive information.
Two cyberthefts targeting the US Office of Personnel Management this year have been widely blamed on China. But the scale of the breach has “very serious implications”.
China Ministry of Foreign Affairs spokesman Hong Lei often has denied that Beijing is involved in hacking and said the country itself is often the victim of such attacks. Clapper said the USA also practices cyberespionage “and we are not bad at it”.
The United States and China, at the conclusion of Chinese President Xi Jinping’s inaugural state visit, agreed to refrain from attacking each other’s critical infrastructure with cyber attacks and to not “conduct or knowingly support cyber-enabled theft of intellectual property”.
He said that what happened in OPM case, “as egregious as it was”, was not an attack. The United States, though it notes the legitimate value of espionage against state targets, has suggested that espionage against private entities and the theft of intellectual property in particular should be “out of bounds”.
“Speaking of the OPM breaches, let me say a couple words about attribution: it is not a simple process and involves at least three related, but distinct determinations: the geographic point of origin, the identity of the actual perpetrator doing the keystrokes, and the responsibility for directing the act”, Clapper said.
Clapper’s remarks drew a sharp response from Senator John McCain, the committee’s chairman.
Last month, President Barack Obama warned China that it could face sanctions for the alleged cybertheft.