How do you block directory scans using htaccess?
From Joomla! Documentation
Add Apache rewrite rules to your .htaccess file. For example, the following will redirect all attempts to access files with names starting with, phpMyAdmin to index.php:
RewriteRule ^/phpMyAdmin.*$ /index.php
Some Regular Expression Tips
^ Means start of filename . Means any character other than newlines * Means one or more of the previous character $ Means end of line