Mandiant Publishes Microsoft 365 Hardening Guidance Against UNC2452

Mandiant published remediation and hardening guidance for Microsoft 365 environments aimed at defending organizations against activity associated with UNC2452, the threat actor tied to high-profile cloud and email compromise operations. The guidance focuses on reducing exposure in Microsoft 365 tenants and helping defenders address weaknesses that can enable persistence, unauthorized access, and abuse of cloud-based identity and messaging services.

The advisory highlights practical steps for security teams to strengthen tenant security, improve detection, and remediate compromise paths in Microsoft 365. For CISOs and defenders, the publication serves as an operational reference for hardening cloud identity, email, and administrative controls against a sophisticated actor known for targeting enterprise and government environments.