Changing the port is effective in some cases, but there are much better solutions for this problem. My favorite is DenyHosts:

http://www.DenyHosts.net

thanks Alan, I have been wondering/looking for a good tool like this. I was even able to install it with yum as it is part of the extras for fedora.

just wondering... what is your opinion of the syncronization feature of this program? It appears a lot of people are allowing/doing it.

Yes, I like the fact that it is part of Fedora Extras also. Similarly, it is included with the CentOS Extras site, which is basically a repository of Fedora Extras packages rebuilt for CentOS:

http://CentOS.Karan.org/

The guy that runs it, Karanbir Singh, is one of the primary CentOS maintainers, so it is a very well-supported and reliable source of packages for CentOS.

I think the synchronization feature is a great idea, and it works well with a few exceptions. For one, if you somehow manage to get one of your own servers denied (for example, see[A HRef="http://www.virtualmin.com/bug-tracker/bug?bug_number=638">Bug #638, it can easily propogate to other servers and block you out from your own systems. You can work around this by adding your own system addresses to the allowed file. You also should read up on the time delay and expiration settings, most of which are set appropriately by default.