Information
This policy setting determines whether Windows can authenticate over a loopback interface.
The recommended state for this setting is: Enabled: Disable authentication over loopback interfaces . Configuring this setting to Disable all authentication protocols and loopback authentication also conforms to the benchmark.
It is best to limit the sign-in interface to only known and trusted services, so malicious actors can't impersonate them.
Solution
To establish the recommended configuration via GP, set the following UI path to Enabled: Disable authentication over loopback interfaces or Disable all authentication protocols and loopback authentication :
Computer Configuration\Policies\Administrative Templates\Center for Internet Security (CIS)\Additional Benchmark Settings\Disable HTTP proxy features: Disable proxy authentication
Note: This Group Policy path is NOT provided by Microsoft. The Group Policy template CIS.admx/adml is included with the CIS Microsoft Windows Build Kits published after January 2026.
Impact:
Windows will not be able to authenticate over a loopback interface