Denyhosts provides a protection against brute force attacks.
Owner: Fedora Infrastructure Team
Contact: #fedora-admin, sysadmin-main group
Purpose: Denyhosts provides a protection against brute force attacks.
All of our servers now implement denyhosts to protect against brute force attacks. Very few boxes should be in the 'allowed' list. Especially internally. Right now lockbox and noc1 are the only two that are explicitly allowed.
Troubleshooting and Resolution
The most common issue will be legitimate logins failing. First, try to figure out why a host ended up on the deny list (tcptraceroute, failed login attempts, etc are all good candidates). Next do the following directions. The below example is for a host (10.0.0.1) being banned. Login to the box from a different host and as root do the following.
cd /var/lib/denyhosts sed -si '/10.0.0.1/d' * /etc/hosts.deny /etc/init.d/denyhosts restart
That should correct the problem.