Preventing access to node/nid paths with .htaccess
With the Drupal module Extended path aliases it is possible to rewrite all node path's including edit & delete paths.
For those that want to prevent access to the regular node/ path, there is a simple Regex Rewriterule with .htaccess possible.
# Redirect all node nid paths
RewriteRule ^node/[0-9]+. http://accessdenied.com [R=301,L]
Take care, 301 is a permanent redirect, cached everywhere. One tiny mistake will take some time to recover from.
302 temporary redirect will make it maybe more fool proof. Just in case...
With the combination of Extended path aliases & this single rewrite line, all your nodes will stay secure and save.