Afternoon,
   I'm the paranoid type and so after installing and setting up my lovely new drupal site I decided that, with all due respect, I'd feel much more comfortable restricting access to the /admin section with an apache password prompt. I'm sure you've done a very good job and adhered to best practices and got it all implemented right but unfortunately my day job involves on-line casinos and lots of other peoples money and hence I am a fully signed-up, card-carrying member of the tin-foil hat wearing security brigade ;^)
   Anyway, I looked about and couldn't find anyone who'd implemented this, not on google or this list so I thought I'd share it with you so that I could get some more eyes over it and in case you wanted to add it to you apache config somewhere..

"
    RewriteEngine on
    RewriteCond %{QUERY_STRING} q=admin [NC,OR]
    RewriteCond %{REQUEST_URI} ^/admin$ [NC]
    RewriteRule (.*) $1 [E=admin_request:1]

    <Files *>
        Order Deny,Allow
        Deny from env=admin_request

        AuthName "Drupal Admin"
        AuthType Basic
        AuthUserFile /somepath/somewhere/apache.htdigest.user

        Require user philip.mather
        Satisfy any
    </Files>
"

...it's not the most trivial of things to implement unless you've used mod_rewrite a fair bit, you'll also need mod_env as well, and perhaps others about to request such a feature will find this before posting. Appologies if this is a repeat or considered off-topic. It should and does (from my testing anyway) catch both the elegant and full URL forms. If anyone spots any problems with it let me know and feel free to re-use it but obviously there's no warranty what-so-ever, you could probably adapt the same to restrict other pages as well I guess.

--
Regards,
Phil