Adversaries may grant additional permission levels to maintain persistent access to an adversary-controlled email account.
For example, the <code>Add-MailboxPermission</code> PowerShell cmdlet, available in on-premises Exchange and in the cloud-based service Office 365, adds permissions to a mailbox.(Citation: Microsoft - Add-MailboxPermission)(Citation: FireEye APT35 2018)(Citation: Crowdstrike Hiding in Plain Sight 2018) In Google Workspace, delegation can be enabled via the Google Admin console and users can delegate accounts via their Gmail settings.(Citation: Gmail Delegation)(Citation: Google Ensuring Your Information is Safe)
Adversaries may also assign mailbox folder permissions through individual folder permissions or roles. In Office 365 environments, adversaries may assign the Default or Anonymous user permissions or roles to the Top of Information Store (root), Inbox, or other mailbox folders. By assigning one or both user permissions to a folder, the adversary can utilize any other account in the tenant to maintain persistence to the target user’s mail folders.(Citation: Remediation and Hardening Strategies for Microsoft 365 to Defend Against UNC2452)
This may be used in persistent threat incidents as well as BEC (Business Email Compromise) incidents where an adversary can add Additional Cloud Roles to the accounts they wish to compromise. This may further enable use of additional techniques for gaining access to systems. For example, compromised business accounts are often used to send messages to other accounts in the network of the target business while creating inbox rules (ex: Internal Spearphishing), so the messages evade spam/phishing detection mechanisms.(Citation: Bienstock, D. - Defending O365 - 2019)
View in MITRE ATT&CK®| Capability ID | Capability Description | Mapping Type | ATT&CK ID | ATT&CK Name | Notes |
|---|---|---|---|---|---|
| ME-MFA-E3 | Multi-factor Authentication | Technique Scores | T1098.002 | Additional Email Delegate Permissions |
Comments
Requiring the use of MFA along with conditional access policies may reduce the likelihood of adversaries making modifications, such as changes to email delegate permissions.
References
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| DEF-IR-E5 | Incident Response | Technique Scores | T1098.002 | Additional Email Delegate Permissions |
Comments
An incident in Microsoft Defender XDR is a collection of correlated alerts and associated data that make up the story of an attack. Microsoft 365 services and apps create alerts when they detect a suspicious or malicious event or activity. Individual alerts provide valuable clues about a completed or ongoing attack. Attacks typically employ various techniques against different types of entities, such as devices, users, and mailboxes. The result of this is multiple alerts for multiple entities in your tenant. Piecing the individual alerts together to gain insight into an attack can be challenging and time-consuming, Microsoft Defender XDR automatically aggregates the alerts and their associated information into an incident. A typical Incident Response workflow in Microsoft Defender XDR begins with a triage action, next is the investigate action, and finally is the response action.
Microsoft 365 Defender Incident Response responds to Additional Email Delegate Permission attacks due to Incident Response monitoring for default alert policies which provides built-in alert policies that help identify Exchange admin permissions abuse and account permissions changes.
License Requirements:
Microsoft Defender XDR
References
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