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.