deny from all - restrict access to directory

To use .htacess files you have to enabled them in your Directory configuration, using AllowOverride All, for example. Of course there are many other options.

To deny all requests for the restricted directory or folder, prepare a .htaccess text file in that directory and put the following directive in it:

deny from all

taken from: http://www.kavoir.com/2009/01/htaccess-deny-from-all-restrict-directory-access.html