New HollowGraph Malware Abuses Microsoft 365 Calendar for C&C Communication

HollowGraph malware is part of a larger toolkit and utilizes a compromised Microsoft 365 account. It abuses the account's calendar as a two-way dead-drop for command and control communication. This approach allows for covert communication between the malware and its operators. The malware's use of a legitimate service like Microsoft 365 Calendar can make it harder to detect. HollowGraph's tactics enable stealthy communication, potentially evading traditional security measures. The malware is a notable example of attackers exploiting cloud services for malicious purposes.