LoFP / assignment of rights to a service account.

Techniques

• T1098

Sample rules

O365 Exchange Suspicious Mailbox Right Delegation

• source: elastic
• technicques:
  • T1098

Description

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.

Detection logic

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)"