secure a database connection string

What’s best way to secure a database connection string?

How to implement database security ?

the absolute, best way, is to vm the frontend and the sql server.

Create the one network that has external access that connects to your webserver, then have another network that only the webserver and sql server share.

Then there is no way to even access the sql server unless you are on the webserver, or a vulnerability in vmware is found.