In this afterdark session, we will show how and demonstrate how we at Hacking-Lab are organizing and running capture-the-flag events. You can also stop by in case you are participating in the CodeMash CTF competition, and need some support. Same if you are trying your luck on the CodeMash t-shirt challenge. Regarding CTFs, we will in particular demonstrate our attack/defense CTF system. With this system, teams have to actually battle against each other (all against all). Each team owns a server with applications on it. The team members have to attack the opponent’s applications, and at the same time, try to protect their own applications. For this purpose, the can change the source code of their applications. The attack/defense system is used for the European Cyber Security Challenge, a competition for cyber security talents all around Europe.