RewriteEngine on
RewriteBase /
RewriteCond %{HTTP_USER_AGENT} ^ Googlebot [OR]
RewriteCond %{HTTP_USER_AGENT} ^ Yandex
RewriteRule ^.*$ - [F]
или
RewriteEngine On
RewriteBase /
RewriteCond %{HTTP_USER_AGENT} -robot
RewriteCond %{REMOTE_ADDR} ^195.48.56.12
RewriteRule ^(.*) for_bad_robots.php