DenyHosts is a python program that automatically blocks ssh attacks 
by adding entries to /etc/hosts.deny. It will also block them via
iptables.  DenyHosts will also inform Linux administrators about
offending hosts, attacked users, and suspicious logins.

Note: the main config file is moved to /etc/denyhosts.conf for
versions greater than 2.6 
Noote: ipaddr-py is a new dependency
DenyHosts has been updated to work with python3 as well as 2, but
will use whichever version is pointed to by /usr/bin/python

to run at start-up, add

# start Denyhosts
if [ -x /etc/rc.d/rc.denyhosts ]; then
  echo "Starting Denyhosts:"
  /etc/rc.d/rc.denyhosts start
fi

to /etc/rc.d/rc.inet2 just after where sshd is run
and make /etc/rc.d/rc.denyhosts executable.