This sounds weird to me. How do they infect a system that they never saw before? Did the wrote the virus on the fly? Or those drones have a common library with a bug or something.
The drones are identical for this competition; and are running an unprotected telnet server on the same wireless network. Just look at the code:
https://github.com/substack/virus-copter
This only proves that the organizers had no technical background whatsoever.
These are the retail standard AR Drones with their own Wifi APs and telnetd enabled. It's not the organizers job to secure them. Would you expect the Defcon organizers to do the same for the attendees?
This is like a Hollywood movie with a bad script