This policy prevents the user from showing account details (email address or user name) on the sign-in screen.
The recommended state for this setting is: 'Enabled'.
Rationale:
An attacker with access to the console (for example, someone with physical access or someone who is able to connect to the server through Remote Desktop Services) could view the name of the last user who logged on to the server. The attacker could then try to guess the password, use a dictionary, or use a brute-force attack to try and log on.
Solution
To establish the recommended configuration via GP, set the following UI path to 'Enabled':
Computer Configuration\Policies\Administrative Templates\System\Logon\Block user from showing account details on sign-in
Note: This Group Policy path may not exist by default. It is provided by the Group Policy template 'Logon.admx/adml' that is included with the Microsoft Windows 10 Release 1607 & Server 2016 Administrative Templates (or newer).
Impact:
The user cannot choose to show account details on the sign-in screen.
18.8.27.1 Ensure 'Block user from showing account details on sign-in' is set to 'Enabled'
Info
Solution