I'm sorry for not replying earlier :) Really, in theory this is very easy. You need a command and control channel, but one that is secured and not abusable. In the first years, I used a CRON job that would pull the configuration files off a load balanced domain. Now, I've upgraded to a self made encrypted P2P version which I really do not want to talk about. However, even if I were to die in a horrible accident, all systems would remain like they are in good condition. This is, like someone mentioned, due to custom repositories that repond to each client uniquely, like someone here suggested. There's no magic to be found here :)