Fully agree with Jooel on this. Have not tried every OS, but would venture to say that EVERY OS if placed on the Internet for access right out of the box, fresh install and no Advanced Admin hardening it, would / could be hacked by someone or some group in a short amount of time.

Also agree that even with hardening, given enough time, persistence, and computing power that probably any OS could be hacked too, but MUCH more difficult and much more time to do so.