Hafnium (group)

Hafnium (sometimes styled HAFNIUM) is a cyber espionage group, sometimes known as an advanced persistent threat, with alleged ties to the Chinese government. 
2021 Microsoft Exchange Server data breach.
Microsoft named Hafnium as the group responsible for the 2021 Microsoft Exchange Server data breach, and alleged they were "state-sponsored and operating out of China". According to Microsoft, they are based in China but primarily use United States-based virtual private servers, and have targeted "infectious disease researchers, law firms, higher education institutions, defense contractors, policy think tanks and NGOs". Investigators outside of Microsoft have not verified the identities or motivations of the group. The Chinese government has denied responsibility for the 2021 Microsoft breach.
The name "Hafnium" was assigned to the group by Microsoft, which publicly disclosed the group's activity on March 2, 2021. Microsoft described the group as "highly skilled and sophisticated".
Capabilities.
In March 2021 it was reported the group had access to the China Chopper web shell, which it has used in the 2021 Microsoft Exchange Server data breach to control hacked servers.