Check: O365-OU-000001
Microsoft Office 365 ProPlus STIG:
O365-OU-000001
(in versions v2 r11 through v2 r4)
Title
The Exchange client authentication with Exchange servers must be enabled to use Kerberos Password Authentication. (Cat II impact)
Discussion
This policy setting controls which authentication method Outlook uses to authenticate with Microsoft Exchange Server. Note: Exchange Server supports the Kerberos authentication protocol and NTLM for authentication. The Kerberos protocol is the more secure authentication method and is supported on Windows 2000 Server and later versions. NTLM authentication is supported in pre-Windows 2000 environments. If you enable this policy setting, you can choose from three different options for controlling how Outlook authenticates with Microsoft Exchange Server: - Kerberos/NTLM password authentication. Outlook attempts to authenticate using the Kerberos authentication protocol. If this attempt fails, Outlook attempts to authenticate using NTLM. This option is the default configuration. - Kerberos password authentication. Outlook attempts to authenticate using the Kerberos protocol only. - NTLM password authentication. Outlook attempts to authenticate using NTLM only. If you disable or do not configure this policy setting, Outlook will attempt to authenticate using the Kerberos authentication protocol. If it cannot (because no Windows 2000 or later domain controllers are available), it will authenticate using NTLM.
Check Content
Verify the policy value for User Configuration >> Administrative Templates >> Microsoft Outlook 2016 >> Account Settings >> Exchange >> Authentication with Exchange Server is set to Kerberos Password Authentication. Use the Windows Registry Editor to navigate to the following key: HKCU\software\policies\microsoft\office\16.0\outlook\security If the value authenticationservice is set to REG_DWORD = 16 (decimal) or 10 (hex), this is not a finding.
Fix Text
Set the policy value for User Configuration >> Administrative Templates >> Microsoft Outlook 2016 >> Account Settings >> Exchange >> Authentication with Exchange Server to Kerberos Password Authentication.
Additional Identifiers
Rule ID: SV-223346r879892_rule
Vulnerability ID: V-223346
Group Title: SRG-APP-000575
Expert Comments
CCIs
Number | Definition |
---|---|
CCI-001967 |
The information system authenticates organization-defined devices and/or types of devices before establishing a local, remote, and/or network connection using bidirectional authentication that is cryptographically based. |
Controls
Number | Title |
---|---|
IA-3 (1) |
Cryptographic Bidirectional Authentication |