http://themarkup.i2p/newsletter/hello-world/lessons-from-a-professional-password-cracker
Compiling RockYou, LinkedIn, Ashley Madison , and other big leaks, we have a really strong picture of people’s passwords. We analyze this data to make more targeted guesses in the future as to what people’s passwords are. It’s a feedback loop; we crack passwords, add them to our word list, and use those to crack new passwords.