RewriteEngine On
RewriteCond  %{HTTP_USER_AGENT}  ^BadBot.*
RewriteRule  .* - [F]


##</code><code>##

RewriteMap robotmap dbm:/path/to/file/map.db

RewriteCond %{HTTP_USER_AGENT} !=""
RewriteCond ${robotmap:%{HTTP_USER_AGENT}|NOT-FOUND}  != NOT-FOUND
RewriteRule .* - [F]