I agree with Mike, but if you must you have to edit your .htaccess file within the library folder. Mainly you don't want to give read access to your
config.php file or to your add-on folders there either. You would probably need to create new .htaccess files in each of the add-on folders to stop it there and then add the code to your .htaccess file in your sites main root directory to protect the config.php file.
The below is what stops it in the library folder.
Deny from all
Then add this to your main .htaccess file in you sites main root directory.
# START CONFIG PROTECTION
deny from all
# END CONFIG PROTECTION