Security through obscurity doesn't work.
It certainly helps defeat most potential intruders but not the most determined. IPtables does help too.
We also run fail2ban at work. Very nice, installs (along with shorewall), and creates a temporary blacklist, blocking an IP that's tried five, I think, times to break in. All configurable, btw.
Here too and from my own systems those 'scriptkiddies' are exposed to the world using http://twitter.com/fail2ban :)
Regards,
Michel