I am not affiliated with this event and nothing I write is authoritative for it.

Originally posted by details
In OpenCTF, teams compete to solve hacking challenges in a wide variety of categories, including web, forensics, programming, cryptography and reverse engineering. There will be challenges for all skill levels, and the contest is open to all DEFCON attendees. More information on how to play can be found at our table and http://openctf.com/, and we will be posting updates on twitter as @open_ctf.
Site: http://www.openctf.com/
Twitter: https://twitter.com/open_ctf