New HollowGraph Malware Uses Microsoft Graph for Stealthy C2 Comms

Microsoft 365 calendars become spy drop boxes in HOLLOWGRAPH campaign

Microsoft 365 calendars have become the latest hiding place for espionage malware, with attackers stashing commands and stolen files inside appointments dated 24 years into the future. Researchers at Group-IB say they've uncovered a malware component they call HOLLOWGRAPH that swaps the usual command-and-control server for something rather less conspicuous – a compromised Microsoft 365 calendar. Instead of reaching out to attacker-controlled inf…

New HollowGraph malware uses Microsoft Graph for stealthy C2 comms

A malicious component dubbed HollowGraph uses the calendar feature in compromised Microsoft 365 mailboxes as a command-and-control channel to receive attacker commands and exfiltrate stolen data.

Hackers Are Turning Microsoft 365 Calendar Invites Into Secret Malware Command Channels

A stealthy new malware strain called HOLLOWGRAPH that hijacks Microsoft 365 calendars to secretly communicate with hackers, disguising malicious commands as ordinary calendar invites. HOLLOWGRAPH is a .NET-compiled malware component that abuses the Microsoft Graph API through a compromised Microsoft 365 account, turning the mailbox’s calendar into a covert two-way “dead drop” for hackers. The malware supports only two commands, get and send, and…

HOLLOWGRAPH malware turns Microsoft 365 calendars into an espionage channel

Microsoft 365 calendars have become a hiding place for espionage malware, with commands and stolen files stashed inside appointments dated to the year 2050, researchers from Group-IB discovered. Targeted campaign tied to Iranian espionage activity The malware, which Group-IB calls HOLLOWGRAPH, is one component of a bigger toolkit the company links with high confidence to the Cavern backdoor framework, a modular espionage toolkit built from separ…

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

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