Here's a good article from SecurityFocus that explains the security philosophy of "Secure by Default." I'd like to add that in addition to OpenBSD and many Linux distributions, Mac OS X has also adopted this philosophy (I believe the other *BSD distros have as well). As the author notes, there are "some interesting changes " with Windows 2003/XP, but, what they essentially amount to is putting up a firewall in front of the services that can't be shut off/closed (due to design flaws relating to RPC).