O365 Exchange Suspicious Mailbox Right Delegationedit
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: 5 minutes
Searches indices from: now-6m (Date Math format, see also Additional look-back time
)
Maximum alerts per execution: 100
Tags:
- Elastic
- Cloud
- Microsoft 365
- Continuous Monitoring
- SecOps
- Configuration Audit
Version: 101 (version history)
Added (Elastic Stack release): 7.16.0
Last modified (Elastic Stack release): 8.6.0
Rule authors: Elastic, Austin Songer
Rule license: Elastic License v2
Potential false positivesedit
Assignment of rights to a service account.
Investigation guideedit
Rule queryedit
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)"
Threat mappingedit
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/
Rule version historyedit
- Version 101 (8.6.0 release)
-
- Formatting only
- Version 100 (8.5.0 release)
-
- Formatting only
- Version 4 (8.4.0 release)
-
-
Updated query, changed from:
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)"
-
- Version 2 (8.1.0 release)
-
-
Updated query, changed from:
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
-