HOLLOWGRAPH Espionage Campaign Exploits Microsoft 365 Calendars — Dallas-Fort Worth Contact-Center and Knowledge-Worker Operations

The HOLLOWGRAPH campaign is actively abusing Microsoft 365 calendar sharing features as covert communication channels, enabling threat actors to exfiltrate data and maintain persistence inside corporate environments without triggering standard email-based detection. Dallas-Fort Worth hosts nearly 790,000 contact-center, back-office, and knowledge-worker seats with deep M365 dependency, making this a high-exposure footprint. Operations leaders should coordinate with IT/security to audit calendar-sharing permissions, enforce conditional access policies, and confirm that SIEM rules cover calendar-based anomalies — particularly on agent and supervisor workstations where M365 is the primary productivity layer.