Security Stack Exchange participation in Capture-The-Flag competitions
Capture The Flag competitions involve setting up a system, usually with some defined but not disclosed vulnerabilities in it, and scoring multiple teams that try to compromise it.
Teams of Security Stack Exchange users participate in some CTF competitions. These will be announced on Security Meta in the ctf. The teams use the CTF chat room to coordinate. This room is private during competitions.
To join the team and get access to the chat room, post a comment on the CTF team announcement question or ping one of the room owners in the main Security chat room. For more information, see the CTF team announcement question.