HOLLOWGRAPH malware turns Microsoft 365 calendars into covert C2 through Microsoft Graph API abuse. Group-IB links it to the Cavern framework. #HOLLOWGRAPH #MicrosoftGraph #Microsoft365 #Malware #C2 #DNSTunneling #Cavern #CyberEspionage http://securityonline.info/hollowgraph-malware-microsoft-graph-api/?utm_source=mastodon&utm_medium=jetpack_social