Suspected Chinese Group Calypso APT Exploiting Vulnerable Microsoft Exchange Servers
released on 2021-03-30 @ 08:52:10 PM
Beginning on March 1, 2021, Recorded Future’s Insikt Group identified a large increase in victim communications to PlugX command and control (C2) infrastructure publicly attributed to the suspected Chinese state-sponsored group Calypso APT. We believe that this activity is highly likely linked to the exploitation of recently disclosed Microsoft Exchange vulnerabilities (also known as ProxyLogon — CVE-2021-26855, CVE-2021-27065). Our observations align with recent reporting by ESET in which the group was identified targeting vulnerable Exchange servers to deploy a web shell and ultimately load the PlugX malware post-exploitation.