Installing DenyHosts on CentOS 5.6

If you have a CentOS server with public IP address, then the server is probably vulnerable to attacks from outside. Brute force attacks are usually done by forcing entry [log in] with the variation of the username and password repeatedly.

What is DenyHosts?

DenyHosts is a script intended to be run by Linux system administrators to help thwart SSH server attacks (also known as dictionary based attacks and brute force attacks).

If you’ve ever looked at your ssh log (/var/log/secure on CentOS) you may be alarmed to see how many hackers attempted to gain access to your server. Hopefully, none of them were successful (but then again, how would you know?). Wouldn’t it be better to automatically prevent that attacker from continuing to gain entry into your system?

Read more on the DenyHosts website:
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Upgrading CentOS 5.5 to CentOS 5.6

Before upgrading CentOS 5.5 to 5.6 it cannot be stressed enough how important it is to make a backup of your system before you do this. Actions listed in this post are written with the assumption that they will be executed by the root user running the bash or any other modern shell.

Clean All Packages

The following command will get a list of packages that are going to be updated.

Upgrade CentOS 5.5 to 5.6

Finally reboot the server for Kernel changes to take effect

Verify that CentOS 5.6 is working: