Hafnium
Microsoft's name for a state-sponsored APT, attributed to China — discovered as the actor behind the ProxyLogon mass exploitation 2021.
Targeted defence contractors, law firms, infectious-disease researchers, think tanks, NGOs. Microsoft attributed publicly 2 March 2021, an unusual move. Now Microsoft uses weather-pattern names ("Hafnium" replaced by "Silk Typhoon" 2023, per the new naming scheme).