After instllation you need to add the following to /etc/hosts.allow:

##	Start here
#---- BlockHosts Additions
#---- BlockHosts Additions

sshd, proftpd, in.proftpd: ALL: spawn (/usr/local/bin/blockhosts.py --verbose --echo "%c-%s" >> /var/log/blockhosts.log 2>&1 )& : allow

##	Stop here

You'll need to do this as root, i.e. type

sudo pico /etc/hosts.allow

or 

sudo edit /etc/hosts.allow

(if you have <a href="http://www.barebones.com/products/textwrangler/index.shtml">TextWrangler</a> installed) in the Terminal.

For additional notes on hosts.allow see the HMUG note on <a href="http://www.hmug.org/HowTos/tcpwrappers.html">TCP Wrappers</a>.