O365 Exchange Suspicious Mailbox Right Delegation
Elastic Stack Serverless Security
Identifies the assignment of rights to accesss content from another mailbox. An adversary may use the compromised account to send messages to other accounts in the network of the target business 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: 1
Rule authors:
- Elastic
- Austin Songer
Rule license: Elastic License v2
The Microsoft 365 Fleet integration, Filebeat module, or similarly structured data is required to be compatible with this rule.
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
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: Exchange Email Delegate Permissions
- ID: T1098.002
- Reference URL: https://attack.mitre.org/techniques/T1098/002/