How do SSIS connection strings send passwords?

I have a SQL server that pulls data from another SQL server via SSIS. We recently converted the server targeted by SSIS to VM. Since the VM conversion I have been getting "login failed for user '(username)'.". errors and the SSIS package fails to run. The connection string of the SSIS package indicates the username (which is correct for the target DB), but I do not see how it passes the password to connect to that DB and pull that data. So how does SSIS send passwords if not in the connection string? The Package Protection Level is set to EncryptAllWithPassword Windows Authorization only option to run.