I downloaded and installed rkhunter 1.3.0. I've been trying to learn more about the linux OS and thought that yum might be easier to use for updating. So... I uninstalled rkhunter and then re-installed it using yum (because I didn't want 2 copies installed).
# yum install rkhunter
is what I typed in and it worked... It installed the system, but I noticed that it only installed 1.2.9. There is a 1.3.0 out and I'm wondering why yum didn't install that one?
Yum will install the latest version that is in the repositories of the distribution, if you want to keep really up to date it is better to install it yourself, specially when it is easy to install as rkhunter.
There are many different repositories but CentOS by default will only use the main CentOS repository. You could try searching google for more, but as someone else said, you may just want to install stuff such as rkhunter by compiling it from source which is fairly easy.