Want to stop users from known blacklisted IP’s from accessing your site? Well, mod_definsible is the apache module for you. Here’s how to install it on Ubuntu:
sudo apt-get install libapache2-mod-defensible
then to enable the module do:
a2enmod defensible
Now create a file in /etc/apache2/mods-available/defensible.conf and put the following couple of lines in it:
DnsblUse On
DnsblServers xbl-bl.spamhaus.org. mydnbl.server.org.
Now restart apache and you’re all set. Now whenever a user that’s on spamhaus’s blocklist tries to access your site, they get a 403 Forbidden page.