An annual event by MWR (cyber security) where we immerse the participants into a world where they must complete various hacking based challenges over the course of several days.  These have included Prisoners in a prison, Soldiers at a Fort and hacking experts in a underground nuclear bunker.

Here's HACKFU as described by MWR: 

 

Describing HackFu isn't easy, just like describing the "HackFu Mind" isn’t. However, if you need a starting point for your understanding you can think of it a cross between an information security conference, a capture the flag competition, a training course and a red team exercise. However, it is a bit of all of these and yet it’s not adequately described by any of them.'