http://www.nsa.gov/selinux/

I just read the documentation regarding SElinux. Is there a way to make my current Mandrake Linux as secure without installing this software?

Just wondering.

Or how could I make ACL more restrictive on my current Linux without SElinux? Meaning, is that could I make some security tweaks to make my documents and files or programs more secure? Basically, how could I restrict (even for 'root') for certain files on Mandrake without using SElinux?

And also OpenBSD, what makes OpenBSD more secure than other Linux or BSD OSs?

i don't know about the securing Mandrake thing, but check this out: http://www.openbsd.org/security.html. *BSDs are amazing and are extremely reliable and secure as server solutions. you should try out a *BSD and play around with it if you get a chance.

OpenBSD has a bunch of stack hardening measures built in by default, as well as a number of security modifications to the gcc compiler that make it compile binaries to be loaded in a very secure manner. It takes forever to explain all the modifications made, but fortunately they wrote a great set of slides that explain all of it. These measures are similar to what the Openwall patch does for Linux.

If you could do all the things that SELinux does without SELinux, then there would be no point to it, would there? Thats why there are so many third-party patches for the Linux kernel to add security. It's also why distros like Red Hat are incorporating SELinux into their kenel. There are several distros out right now that do have the Openwall patches applied by default.