Elastic Security Detection Rules

O365 Exchange Suspicious Mailbox Right Delegation

Last updated 3 days ago on 2025-04-01
Created 4 years ago on 2021-05-17

About

Identifies the assignment of rights to access content from another mailbox. An adversary may use the compromised account to send messages to other accounts in the network of the target organization while creating inbox rules, so messages can evade spam/phishing detection mechanisms.
Tags
Domain: CloudData Source: Microsoft 365Use Case: Configuration AuditTactic: PersistenceLanguage: kuery
Severity
low
Risk Score
21
MITRE ATT&CK™

Persistence (TA0003)(opens in a new tab or window)

↳ Account Manipulation (T1098)(opens in a new tab or window)

False Positive Examples
Assignment of rights to a service account.
License
Elastic License v2(opens in a new tab or window)

Definition

Rule Type
Query (Kibana Query Language)
Integration Pack
Prebuilt Security Detection Rules
Index Patterns
filebeat-*logs-o365*
Related Integrations

o365(opens in a new tab or window)

Query
event.dataset:o365.audit and event.provider:Exchange and event.action:Add-MailboxPermission and
o365.audit.Parameters.AccessRights:(FullAccess or SendAs or SendOnBehalf) and event.outcome:success and
not user.id : "NT AUTHORITY\SYSTEM (Microsoft.Exchange.ServiceHost)"

Install detection rules in Elastic Security

Detect O365 Exchange Suspicious Mailbox Right Delegation in the Elastic Security detection engine by installing this rule into your Elastic Stack.

To setup this rule, check out the installation guide for Prebuilt Security Detection Rules(opens in a new tab or window).