The Biden administration is undertaking a “whole of government response” to investigate and respond to the cyberattacks against Microsoft’s Exchange Server, which the Big Tech company assessed are being carried out by a sophisticated Chinese state-backed hacker group.

Microsoft announced it detected “multiple zero-day exploits being used to attack on-premises versions of Microsoft Exchange Server in limited and targeted attacks” last week and said its Threat Intelligence Center attributed the cyber campaign with “high confidence” to a hacker group dubbed “Hafnium.” Microsoft said the hacker group was “state-sponsored” and operating out of China.