I was hanging out in the CTF room today at DEFCON enjoying the hilarious videos being projected when I suddenly wondered what OS most guys were running. A cursory glance revealed quite a spread, so I decided to take a lighting-fast poll.
[ Note: these numbers are not really accurate. I got them very quickly while trying not to annoy people who were in many cases very busy. ]
Everything from Plan 9 to Windows 2000.
[ Many people were running multiple OSs, so each was counted. ]
OS X 
Windows 7 
Windows XP 
Windows 2000 
Plan 9 
So, a few observations:
First, Linux is king here. There were a ton of Macbooks and Macbook Pro’s (roughly 25% of the mix, I’d say), but most of them were running Linux.
It was interesting to see all version of Windows, from 2000 to Windows 7 being used.
The reason people gave for running so many operating systems was pretty intuitive for anyone who’s done pentesting: It’s best to attack a given OS from that same OS. And there were a number of tests that required a certain OS, e.g. FreeBSD.
The team that appeared to be all Asians was nearly 100% Windows 7. I thought that was interesting, and it matches what I’ve heard elsewhere (I have a buddy in Korea who says Linux and OS X have virtually no penetration there).
The VedaGodz team was significantly made up of Mac hardware, but they were running nothing but Linux. They also seemed to be doing very well.
That’s about it. Linux took the representation cake (no surprise there), hackers love Apple hardware, and Asians prefer Windows. Throw in some IRIX, Plan 9, and Windows 2000 machines, and you’ve got a DEFCON CTF room. ::
1 I cannot stress enough how non-scientific this polling was. Any team who wants to give better numbers, feel free and I’ll update the list.2 Serious respect to the DDTEK group for the music and video content in the CTF room. That’s one of my favorite things about the con, actually.