A wargame is a computer security game where you play the role of an attacker. I have created ten wargames in the form of virtual machines that you download and run on your local machine.
You are then given a task such as "gain root" or "deface the website" and this is possible using some exploitation technique.
If this sounds interesting to you you may also want to take a look at my Sourceforge project at http://sourceforge.net/projects/ctfd/.
You can probably run the wargames using most virtual machine managers but I recommend Qemu which is also the one I used during development.
Find the individual wargames through the menu under Security->Wargames.