i dont know if any of you have looked thru the rpmup script but basically it\'s doing the same thing as up2date. It downloads all packages that updates.redhat.com releases for your distro except that it doesnt use updates.redhat.com. It uses updates.cpanel.net which looks to me like the mirrored updates.redhat.com
I kinda modified the rpmup script a bit for testing purposes to use my own mirror or updates.redhat.com for updating systems that arnt using cpanel. I dont know if this is illegal (is it nick?) but it works great. I maily use it to update dedicated servers out their that are running just a base install and configured the system on their own. i just told it to ignore most packages like apache, mysql, kernel, postsql, etc.
Up2date is alittle more complexe i beleive because it checks for dep\'s and will also download other packages that are needed say if you do a up2date install blah but then again who wants to register every machine with RHN not to mention that you can use their web interface to log in and add/remove packages from your machine from their website!!!!! You dont even have to have the root pass. I was extremely PIST when i found this out and i let them know it. It\'s bull**** in my opinion (sorry for the language).
2 things to help secure your server... update the kernel and maybe setup a firewall closing all ports that your dont need.