Welcome, young hacker.

Qualifying to DEF CON CTF 2020

Everyone will have a chance to qualify through our online event on March 27th!

Start practicing now, either by solving our old challenges or by playing in awesome CTFs.


Winning one of the pre-qualifying CTF events will also get you to the finals. Keep an eye on our twitter account for announcements.

The first event has been selected: CODE BLUE. Congratulations to the winners, CyKOR, first to pre-qualify!

The second event, HIT CON CTF, has also been selected.

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.

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.