A Chinese cybersecurity firm has been sanctioned by the US Department of the Treasury’s Office of Foreign Assets Control (OFAC) for alleged links to the notorious hacking group Salt Typhoon.

The U.S. Treasury Department on Friday imposed sanctions on alleged hacker Yin Kecheng and cybersecurity company Sichuan Juxinhe Network Technology Co., accusing both of being involved in a series of hacks against American telecom companies.

US Treasury Secretary Janet Yellen’s computer was infiltrated and unclassified files were accessed as part of a broader breach of the agency by Chinese state-sponsored hackers, according to two people familiar with the matter.