THIS IRANIAN MALWARE HAS NO C2 SERVER TO BLOCK. THE COMMAND CHANNEL IS A MEETING INVITE IN YOUR OWN CALENDAR

Summary from the TLDR InfoSec newsletter

HollowGraph is an Iranian-nexus malware tied to the Cavern backdoor framework that runs no command-and-control infrastructure at all and instead reads orders from and writes stolen data into a victim's own Microsoft 365 calendar over the legitimate Graph API. The implant encrypted its traffic with a hybrid RSA plus AES-256-GCM scheme using separate key pairs per direction and exfiltrated Entra ID credentials via DNS tunneling. Group-IB counted twelve infected Israeli systems active between June 3 and July 9. It linked the malware to the Lyceum espionage cluster, and Check Point separately documented the same Cavern framework this month under the name Cavern Manticore.