There are different ways to do that. One solution could be access over https.
You set up a webserver with a simple webappkicaton. The app returns a html table containing only the customers data. Authentiction (Ssl) can be done in a secure way by passwort or TLS.
Authorisation can be handled either in the webserver or in the application.
Importing records from a html table works very well in QlikView, but ist depends a little bit on the size.
HTH