[support] how to make drupal admin section https only?

[dondi_2006]

Greetings,

I've just realized that (at least with default settings)
the admin section of a drupal website is accessible
via normal http, that is, I guess also the password
when I login is transmitted in plain text.

How do I make sure that all admin pages and those only,
are sent via https, and that username and passwords are
sent encrypted from the browser?

TIA,
O.