We have recently expanded the integration of Antimalware Scan Interface (AMSI) with Office 365 to include the runtime scanning of Excel 4.0 (XLM) macros, to help antivirus solutions tackle the increase in attacks that use malicious XLM macros.
Microsoft has detected multiple 0-day exploits being used to attack on-premises versions of Microsoft Exchange Server in limited and targeted attacks. In the attacks observed, threat actors used this vulnerability to access on-premises Exchange servers, which enabled access to email accounts, and install additional malware to facilitate long-term access to victim environments. Microsoft Threat Intelligence Center (MSTIC) attributes this campaign with high confidence to HAFNIUM.
