yes, this is something that can be done,

in the admin area, go to your page which you need to protect, then on the access tab, select the user group.

thats it.

I have a follow up question regarding this. I see that once you password protect a page, then that page doesn't appear on the site at all. Is it possible to actually show the page (as a list or menu item) but assign it an icon (perhaps a padlock) that shows that the page will require a login in order to access?

Alternatively, how do you request that the visitor logs in? Is there a pre-defined Silverstripe page that is already built to permit internal users to submit their credentials thereby permitting access to pages that they're allowed to read. From what I can see, the only password page that Silverstripe has is the main admin page?