The Login page is editable, you just need to select the display with name LogOn to edit its layout. As you can see in the code behind of that display, it calls the method Security.Logon() to do the validation of the user. If you want to perform any other user validation, you just need to modify that logic calling your own validation system and then calling the LogOn method, according to the results of your validation.

Another way to customize the logon is to put your own custom logic on the ClientStartup script task. The script is executed on any computer that is connecting to the server application, you can perform verifications based on computer IP, computer name, Windows Active-Directory Logged user, or any other criteria to specify if the user is allowed to start the application and which should be their credentials, after that you can either call client.Shutdown to terminate the application if it was an unauthorized access or Security.Logon() with a user that matches the selected security profile.

By default, when starting the application on a client computer, instead of requesting a login, we start the system with the user GUEST. The user Guest is equivalent to an anonymous login, if you don’t want that on your application, just replace the startup page with a page requesting the Logon information.