Attribution of OPM attack still being debated
Proving attribution for the OPM attack is no easy task and involves determining three issues: the geographic point of origin (typically disguised); the author identity (analyzing the individuals' keystrokes); and finally working out who authorised the attack. According to National Intelligence Director James Clapper, there are "differing degrees of confidence" as to who might actually have been responsible.  In a side remark Clapper said that whilst the Chinese were responsible for the greatest volume of attacks, the Russian's modus operandi was far smarter. Meanwhile, the Washington Post reveals that the CIA withdrew a number of people from its Chinese operations due to identification risk from the OPM hack.

WASHINGTON (Sputnik) — The process of finding the perpetrators who hacked into the US Office of Personnel Management (OPM) continues to be fraught with challenges, National Intelligence Director James Clapper told the US Senate Armed Services Committee on Tuesday.

"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.

In April, the US government acknowledged that a massive cyberattack on OPM networks has compromised the personal information of more than 21 million former and current federal employees. Moreover, the fingerprints data of some 5.6 million people has also been stolen.