SolarWinds: FireEye Offers Remediation Strategies and Auditing Tool
FireEye has published a white paper, Remediation and Hardening Strategies for Microsoft 365 to Defend Against UNC2452, as well as a tool, Mandiant Azure AD Investigator, "for detecting artifacts that may be indicators of UNC2452 and other threat actor activity."
Check the results of the FireEye tool against your current tool output to avoid blind spots.
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FireEye: Remediation and Hardening Strategies for Microsoft 365 to Defend Against UNC2452 (White paper PDF)
Gov Infosecurity: Free Auditing Tool Helps Detect SolarWinds Hackers' Malware