have something like this in your .htaccess...
1.)
RewriteCond %{HTTP_USER_AGENT} ^.*Crawler.*$ [OR]
RewriteCond %{HTTP_USER_AGENT} ^.*Snagger.*$ [OR]
RewriteCond %{HTTP_USER_AGENT} ^.*Teleport.*$ [OR]
RewriteCond %{HTTP_USER_AGENT} ^.*Reaper.*$ [OR]
RewriteCond %{HTTP_USER_AGENT} ^.*Wget.*$ [OR]
RewriteCond %{HTTP_USER_AGENT} ^.*Grabber.*$ [OR]
RewriteCond %{HTTP_USER_AGENT} ^.*Sucker.*$ [OR]
RewriteCond %{HTTP_USER_AGENT} ^.*Downloader.*$ [OR]
RewriteCond %{HTTP_USER_AGENT} ^.*Siphon.*$ [OR]
RewriteCond %{HTTP_USER_AGENT} ^.*Collector.*$ [OR]
RewriteCond %{HTTP_USER_AGENT} ^.*Mag-Net.*$
RewriteRule /*
http://www.noscripts.com/ [L,R]
(list not complete)
2.)
change the name of your member dirs dynamically
3.)
use session management and update your .htaccess every 10 min, delete expired sessions out of the .htpasswd...