Mailbox Client Access Setting (CAS) changed

Synopsis

Field	Value
Activation Period	14 Days
Training Period	30 Days
Test Period	N/A (single event)
Deduplication Period	1 Day
Required Data	Requires one of the following data sources: Windows Event Collector OR XDR Agent with eXtended Threat Hunting (XTH)
ATT&CK Tactic	Collection (TA0009)
ATT&CK Technique	Data Staged: Local Data Staging (T1074.001)
Severity	Medium

Description

An attacker may use PowerShell to change the Client Access Settings (CAS) for a mailbox, hence gaining access to the data.

Attacker's Goals

Gain access to the data in the compromised mailbox.

Investigative actions

• Examine the PowerShell command to identify which mailbox's access setting has been modified.
• Verify that the change in the client access setting was executed by a trusted source.