HollowGraph Malware Hides C2 and Stolen Files in Microsoft 365 Events Dated 2050

1Key Takeaways

• A newly discovered espionage implant has been using a hijacked Microsoft 365 calendar as its command channel, planting operator instructions and smuggling out stolen files as attachments on calendar events dated to the year 2050.
• Group-IB, which named the malware HollowGraph, says the approach moves tasking and stolen data through legitimate Microsoft Graph API traffic, so the activity looks.