Guest account (Windows)
Disable the Windows™ Guest account to prevent anonymous logins.
By default, the Windows Guest account is disabled. If you enable the Guest account, remote and local users can connect to the database server anonymously. Disable the Guest account in the Windows Control Panel. Also, set the configuration parameter SECURITY_LOCAL_CONNECTION = 1 to prevent local users from connecting by specifying a user name that is different from the user who is running the client process.