Detections
Analytics
1.13.3.3.7 Ensure 'Configure Outlook object model prompt when sending mail:' is set to Enabled:Automatically Deny
Information
This policy setting controls what happens when an untrusted program attempts to send e-mail programmatically using the Outlook object model.If you enable this policy setting, you can choose from four different options when an untrusted program attempts to send e-mail programmatically using the Outlook object model:
- Prompt user - The user will be prompted to approve every access attempt.
- Automatically approve - Outlook will automatically grant programmatic access requests from any program. This option can create a significant vulnerability, and is not recommended.
- Automatically deny - Outlook will automatically deny programmatic access requests from any program.
- Prompt user based on computer security. Outlook will only prompt users when antivirus software is out of date or not running.
Important: This policy setting only applies if the ''Outlook Security Mode'' policy setting under ''Microsoft Outlook <version>\Security\Security Form Settings'' is configured to ''Use Outlook Security Group Policy.''
If you disable or do not configure this policy setting, when an untrusted application attempts to send mail programmatically, Outlook relies on the setting configured in the ''Programmatic Access'' section of the Trust Center. The recommended state for this setting is: Enabled:Automatically Deny.
Rationale:
If an untrusted application programmatically sends e-mail, that application could send mail that includes malicious code, impersonate a user, or launch a denial-of-service attack by sending a large volume of mail to a user or group of users.
By default, when an untrusted application attempts to send mail programmatically, Outlook relies on the setting configured in the 'Programmatic Access' section of the Trust Center. This setting determines whether Outlook will warn users about programmatic access attempts:
* Only when antivirus software is out of date or not running (the default setting)
* Every time
* Not at all
If the 'Not at all' option is selected, Outlook will silently grant programmatic access to any program that requests it, which could allow a malicious program to gain access to sensitive information.
Note: This described default functionality assumes that you have not followed the recommendation to enable the 'Outlook Security Mode' Group Policy setting to ensure that Outlook security settings are configured by Group Policy. If Group Policy security settings are used for Outlook, the 'Programmatic Access' section of the Trust Center is not used. In this situation, the default is to prompt users based on computer security, which is the equivalent of the 'Only when antivirus software is out of date or not running' option in the Trust Center, and the user experience is not affected.
Solution
To implement the recommended configuration state, set the following Group Policy setting to Enabled.User Configuration\Administrative Templates\Microsoft Outlook 2016\Security\Security Form Settings\Programmatic Security\Configure Outlook object model prompt when sending mail
Then set the Configure Outlook object model prompt when sending mail: Guard behavior: option to Automatically Deny.
Impact:
Enabling this setting and selecting Prompt user based on computer security enforces the default configuration in Outlook, and therefore is unlikely to cause usability issues for most users.
Important: If this setting is enabled, you must also enable the 'Outlook Security Mode' setting in User Configuration\Administrative Templates\Classic Administrative Templates (ADM)\Microsoft Office Outlook <version>\Security\Security Form Settings\Microsoft Office Outlook Security and select Use Outlook Security Group Policy from the drop-down list.
See Also
Item Details
Audit Name: CIS Microsoft Office Outlook 2016 v1.1.0 Level 1
Category: CONFIGURATION MANAGEMENT
References: 800-53|CM-6b.
Plugin: Windows
Control ID: 9d79e8f5f127afd1d851197dd34258d48d0dfdfb69cfeb63cbd39c19bdb25286