This metric checks whether your SQL Server installation is using the default TCP port.
It’s widely known that SQL Server 2005 and 2008 listen on TCP port 1433. Keeping this default gives hackers a potential way of attacking your server.
This alert is raised when you are using the default port of 1433 which is a known security risk. You should consider modifying the port to a non-standard, non-default port in order to thoroughly secure your systems.
For information on how to change the TCP a server listens on, see MSDN.