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Malware

HOLLOWGRAPH: Abusing Microsoft 365 Calendars for Covert C2

July 20, 2026

HOLLOWGRAPH is a .NET NativeAOT-compiled DLL that abuses Microsoft Graph API to use Microsoft 365 calendar events as a two-way dead-drop for C2 communication and data exfiltration, with events dated in the far future to avoid detection.