If you are using Ubuntu 12.04 and the "ufw" firewall configuration tool, then you may want to consider this pre-configured package. It includes the "framework" perl client for iptables with some adjustments to make it work easier with Ubuntu 12.04. You do need to install the "dialog" and the "mailutils" package if you don't have them already installed.
Prerequisites Step by Step Install instructions:
$ sudo apt-get install dialog
$ sudo apt-get install mailutils
Installing the DShield client:
$ wget http://isc.sans.edu/clients/dshieldufw.deb
$ sudo dpkg -i dshieldufw.deb
this will launch a dialog asking you for the e-mail address and numeric DShield user id. You can find this after logging in to DShield.
A PGP signature for the package can be found at dshieldufw.deb.asc
