Microsoft 365 mailbox audit logging bypass
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Goal
Detect when a user configures a mailbox audit logging bypass.
Strategy
Monitor Microsoft 365 Exchange audit logs to look for the operation Set-MailboxAuditBypassAssociation. When this operation is configured, no activity is logged, such as a user or account accessing or taking other actions in a mailbox. Attackers may configure this setting to evade existing defenses.
Triage and response
- Inspect the
@Parameters.Identity attribute to determine which user or account will bypass mailbox audit logging. - Determine if there is a legitimate use case for the mailbox audit bypass by contacting the user
{{@usr.email}}. - If
{{@usr.email}} is not aware of the mailbox audit bypass:- Investigate other activities performed by the user
{{@usr.email}} and @Parameters.Identity using the Cloud SIEM - User Investigation dashboard. - Begin your organization’s incident response process and investigate.
Changelog
- 17 August 2023 - Updated query to replace attribute
@threat_intel.results.subcategory:tor with @threat_intel.results.category:tor.
