Hacker “Capture the Flag” has been a mainstay at hacker gatherings since the mid-1990s. It’s like the outdoor game, but played on computer networks. Teams of hackers defend their own computers while attacking other teams’. It’s a controlled setting for what computer hackers do in real life: finding and fixing vulnerabilities in their own systems and exploiting them in others’. It’s the software vulnerability lifecycle.

These days, dozens of teams from around the world compete in weekend-long marathon events held all over the world. People train for months. Winning is a big deal. If you’re into this sort of thing, it’s pretty much the most fun you can possibly have on the Internet without committing multiple felonies…