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M365 Exchange Inbox Rule with Obfuscated Name

Identifies when a Microsoft Exchange inbox rule is created or modified with a name composed only of special characters. Adversaries may use obfuscated inbox rule names to evade detection, hide malicious forwarding or…

Description

Identifies when a Microsoft Exchange inbox rule is created or modified with a name composed only of special characters. Adversaries may use obfuscated inbox rule names to evade detection, hide malicious forwarding or deletion rules, or blend in with benign audit noise. The rule name is parsed from "o365.audit.ObjectId", which encodes the mailbox identity and rule name separated by a backslash.

Detection logic

Its licence does not clear it for publishing here

Sunturai publishes a detection's own text where the licence it arrived under has been reviewed and permits it, and Elastic License 2.0 has not. The query as its source wrote it, its canonical form and the hash that pins this revision are in the workspace record.

Detection requirements

Platform
ESXiLinuxmacOSOffice SuiteWindows

The rule states no platform. This is derived from the 2 ATT&CK techniques it maps to.

Known benign triggers

  • Rare legitimate automation or third-party tools may create inbox rules with non-alphanumeric names. Validate against known messaging workflows and approved admin scripts before escalating.

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