Welcome, young hacker.

Congratulations PPP, winner of DEF CON CTF 2019! Scores and other info here.

Players, it was an honor to play with you. Everyone, we hope you enjoyed our work and will play next year. Join a team, win one of the awesome pre-qualifying CTF events, or play our online qualifier.

Call for pre-qualifiers

What events will pre-qualify me, you ask? We want to know too!

If your CTF is high-quality, well-regarded, and compatibile with our philosophy, heed our call

Nominations will be looked at shortly after submission, and the OOO will announce the selection of events on a first-selected, first-announced basis. Act fast: the first event, CODE BLUE, has already been selected.

Who are we?

We are the Order of the Overflow. We are the current host of DEF CON CTF (Quals and Finals). Read about our philosophy here or reach us at

Twitter: Follow @oooverflow on Twitter for updates!


Open source releases: github/o-o-overflow

Thanks and sponsors

People and organizations to which we owe thanks are listed here.