Fedora :: Make 'yum Update' On CentOS Recurring And Automatic?

I run a few dozen dedicated web servers all running CentOS 5.5. A long time ago when one server was apparently compromised, I was urgently advised to sign in to the server and run "yum update" at least once a week to ensure that everything which I had installed using "yum", would get updated with any recently available updates, including security fixes, and that one reason I might have been hacked before was because I hadn't been doing that.

So, I'm still not sure if that would have prevented the original break-in, or how much this has reduced my chances of being hacked, but I've been faithfully signing in to each server every week for the past few months and running "yum udpate". Most times, this results in a lot of patches being downloaded and applied, so it's clear the machines are not doing it automatically. I figure it's about time to learn how to make the machines do this on their own. Is there a standard way to make "yum update" run automatically, every day, or every week? Yes, I'm sure there are many ways to do it, but is there a single way used by the majority of webmasters of CentOS sites who have automatic updates set up? Googling a bit for "make yum updates automatic" turned up some threads like:

[code]...

in which people describe writing their own custom scripts to do yum update automatically. This seems odd. It seems like the kind of thing that there would be a standard way to turn on. Also, is there a reason that virtually every newly provisioned dedicated server does not have "yum update" set up to recur automatically? If it's true that people break into websites using exploits that have been found in older versions of webservers and other software, and that sometimes these breakins would have been prevented by the newest patches, wouldn't it reduce the number of websites being compromised if the OS had yum updates turned on automatically by default?