(Reuters) -U.S. Treasury Secretary Janet Yellen's computer was hacked and unclassified files were accessed as part of a broader breach of the Treasury Department by Chinese state-sponsored hackers, Bloomberg News reported on Thursday, citing two people familiar with the matter.
The computers of two of Yellen's lieutenants, Deputy Secretary Wally Adeyemo and Acting Under Secretary Brad Smith, were also breached, the report said.
The hackers accessed fewer than 50 files on Yellen's machine, Bloomberg said.
The Treasury Department did not immediately respond to a Reuters' request for a comment.
The hack, what the Treasury called a "major incident", happened in December when Chinese state-sponsored hackers breached the department's computer security guardrails by compromising third-party cybersecurity service provider BeyondTrust, according to Treasury officials.
"China has always opposed all forms of hacker attacks," Mao Ning, a spokesperson for China's foreign ministry, said at the time.