Along with a large group of allies, including the EU and NATO, the U.S. government blamed a broad "pattern of malicious cyber activity" on China.
A statement issued by the White House on July 19 says that the Biden administration is "aware that [People's Republic of China] government-affiliated cyber operators have conducted ransomware operations against private companies that have included ransom demands of millions of dollars." It also says with "a high degree of confidence" that hackers affiliated with China's Ministry of State Security recently exploited vulnerabilities in Microsoft Exchange "to compromise tens of thousands of computers and networks worldwide."
The Department of Justice also announced "criminal charges against four MSS hackers addressing activities concerning a multiyear campaign targeting foreign governments and entities in key sectors, including maritime, aviation, defense, education, and healthcare in [at] least a dozen countries."