Fail2ban is an intrusion prevention framework which scans the log files on your system (such as: var/log/secure) and spots repeated password failures.
Too many failures, and it will update your firewall to drop all traffic from the offending IP address. Pretty handy, and enough to stop the casual hacker with a dictionary attack.
Fail2ban is very flexible and can be configured to work with any service that writes to a logfile, but here's the basics to get you up and protected in a few minutes.
1. Get the files
cd to /tmp for a nice place for them to land, then
2. Extract them
tar -xf fail2ban-0.8.4.tar.bz2
3. Head to the new directory and install
then (you need to have python installed)...
python setup.py install
All installed ok?
4. Get it starting up automatically
cp files/redhat-initd /etc/init.d/fail2ban
chkconfig --add fail2ban
chkconfig fail2ban on
You'll need to turn some stuff on, and fiddle with settings to your liking in:
If you're enabling SSH-iptables, then the path for SSH monitoring needs to be changed to /var/log/secure
You can determine the services being monitored, number of retries a user is allowed, as well as the ban time in this settings file.
Once you're configured, start the service with:
service fail2ban start
And you're done.