O365 Exchange Suspicious Mailbox Right Delegation
Elastic Stack Serverless Security
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.
Rule type: query
Rule indices:
- filebeat-*
- logs-o365*
Severity: low
Risk score: 21
Runs every: 5m
Searches indices from: None (https://www.elastic.co/guide/en/elasticsearch/reference/current/common-options.html#date-math[Date Math format], see also Additional look-back time)
Maximum alerts per execution: 100
References: None
Tags:
- Elastic
- Cloud
- Microsoft 365
- Continuous Monitoring
- SecOps
- Configuration Audit
Version: 4
Rule authors:
- Elastic
- Austin Songer
Rule license: Elastic License v2
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)"
Framework: MITRE ATT&CKTM
Tactic:
- Name: Persistence
- ID: TA0003
- Reference URL: https://attack.mitre.org/tactics/TA0003/
Technique:
- Name: Account Manipulation
- ID: T1098
- Reference URL: https://attack.mitre.org/techniques/T1098/
Sub-technique:
- Name: Additional Email Delegate Permissions
- ID: T1098.002
- Reference URL: https://attack.mitre.org/techniques/T1098/002/